Human aflatoxin B1 aldehyde reductase

ABSTRACT

The invention provides a human aflatoxin B1 aldehyde reductase (AFB1-hAR) and polynucleotides which identify and encode AFB1-hAR. The invention also provides expression vectors, host cells, agonists, antibodies and antagonists. The invention also provides methods for treating disorders associated with expression of AFB1-hAR.

This application is a divisional application of U.S. application Ser.No. 08/907,674, filed Aug. 8, 1997.

FIELD OF THE INVENTION

This invention relates to nucleic acid and amino acid sequences of ahuman aflatoxin B1 aldehyde reductase and to the use of these sequencesin the diagnosis, prevention, and treatment of gastrointestinal andneoplastic disorders.

BACKGROUND OF THE INVENTION

Aflatoxin B1 (AFB1) is a potent environmental carcinogen produced by thecommon molds Aspergillus flavus, A. parasiticus, and A. nominus. Humanexposure results principally from the ingestion of stored foodstuffscontaminated with these molds. Carcinogenicity is associated with theconversion of AFB1 to its 8,9-oxide by the hepatic cytochromeP450-dependent monooxygenase system. Ingestion of food contaminated withfungal aflatoxins is believed to contribute to the high incidence ofhepatoma and chronic liver disease in subtropical regions.

Hayes, J. D. et al. (1993; Cancer Res. 53:3887-3894) reported thatexpression of an aldehyde reductase (AR) is induced in the liver of ratsfed on an ethoxyquin-containing diet. Ethoxyquin activates transcriptionof several liver detoxification enzymes. Induction of expression of thealdehyde reductase is correlated with resistance to AFB1-inducedcarcinogenesis. The enzyme, AFB1 -AR, catalyzes the formation of adialcohol from the cytotoxic dialdehyde form of AFB1-8,9-dihydrodiol(Judah, D. J. et al. (1993) Biochem J. 292:13-18). Ellis, E. M. et al.(1993; Proc. Natl. Acad. Sci. USA 90:10350-10354) isolated cDNA whichencodes AFB1-AR and observed that the AFB1-AR protein sequence defines apreviously unrecognized subclass of the aldehyde reductase superfamily.AFB1-AR is 327 amino acids in length and contains a putative active sitehistidine at position 109.

Primary hepatocellular carcinoma (HCC) occurs with high frequency ineastern Asia and sub-Saharan Africa. In these areas of the world,chronic hepatitis B virus (HBV) infection is the best described riskfactor for HCC; however, only 20-25% of HBV carriers develop HCC(McGlynn, K. A. et al. (1995) Proc. Natl. Acad. Sci. USA 92:2384-2387).In certain areas of the HCC endemic regions, an unusual mutational hotspot has been reported in the p53 tumor suppressor gene. This mutation,at codon 249 in exon 7, is an AGG-to-AGT transversion (arginine toserine). The geographic distribution of these mutations and thesimilarity of these mutations to the transversions produced in vitro byAFB1 suggest that exposure to AFB1 causes the p53 mutation.Demonstration of the preferential mutability of p53 codon 249 by ratliver microsome-activated AFB1 in HepG2 cells supports this hypothesis(Aguilar, F. et al. (1993) Proc. Natl. Acad. Sci. USA 90:8586-8590).

AFB1 is metabolized and detoxified in the liver via detoxificationpathways. McGlynn et al. (supra) proposed that genetic variation in AFB1detoxification genes may define susceptibility to the effects of AFB .To test their hypothesis, genetic variation in two AFB1 detoxificationgenes, epoxide hydrolase (EPHX) and glutathione S-transferase M1(GSTM1), was compared with the presence of serum AFB1-albumin adducts,the presence of hepatocellular carcinoma (HCC), and with p53 codon 249mutations. Mutant alleles at both loci were significantlyover-represented in individuals with serum AFB1-albumin adducts in across-sectional study. In a case-control study mutant alleles of EPHXwere significantly overrepresented in persons with HCC. The relationshipof EPHX to HCC varied by hepatitis B surface antigen status andindicated that a synergistic effect may exist. p53 codon 249 mutationswere observed only among HCC patients with one or both high-riskgenotypes. These results indicate that individuals with mutant genotypesat EPHX and GSTM1 may be at greater risk of developing AFB1 adducts, p53mutations, and HCC when exposed to AFB1. Hepatitis B carriers with thehigh-risk genotypes may bear even greater risk than carriers withlow-risk genotypes. These findings by McGlynn et al. (supra) support theexistence of genetic susceptibility in humans to the environmentalcarcinogen AFB1 and indicate that there is a synergistic increase inrisk of HCC with the combination of hepatitis B virus infection andsusceptible genotype.

The discovery of a new human aflatoxin B1 aldehyde reductase and thepolynucleotides encoding it satisfies a need in the art by providing newcompositions which are useful in the diagnosis, prevention and treatmentof gastrointestinal and neoplastic disorders.

SUMMARY OF THE INVENTION

The invention features a substantially purified polypeptide, humanaflatoxin B1 aldehyde reductase (AFB1-hAR), having the amino acidsequence shown in SEQ ID NO:1, or fragments thereof.

The invention further provides an isolated and substantially purifiedpolynucleotide sequence encoding the polypeptide comprising the aminoacid sequence of SEQ ID NO:1 or fragments thereof and a compositioncomprising said polynucleotide sequence. The invention also provides apolynucleotide sequence which hybridizes under stringent conditions tothe polynucleotide sequence encoding the amino acid sequence SEQ IDNO:1, or fragments of said polynucleotide sequence. The inventionfurther provides a polynucleotide sequence comprising the complement ofthe polynucleotide sequence encoding the amino acid sequence of SEQ IDNO:1, or fragments or variants of said polynucleotide sequence.

The invention also provides an isolated and purified sequence comprisingSEQ ID NO.2 or variants thereof. In addition, the invention provides apolynucleotide sequence which hybridizes under stringent conditions tothe polynucleotide sequence of SEQ ID NO:2. The invention also providesa polynucleotide sequence comprising the complement of SEQ ID NO:2, orfragments or variants thereof.

The present invention further provides an expression vector containingat least a fragment of any of the claimed polynucleotide sequences. Inyet another aspect, the expression vector containing the polynucleotidesequence is contained within a host cell.

The invention also provides a method for producing a polypeptidecomprising the amino acid sequence of SEQ ID NO:1 or a fragment thereof,the method comprising the steps of: a) culturing the host cellcontaining an expression vector containing at least a fragment of thepolynucleotide sequence encoding AFB1 -hAR under conditions suitable forthe expression of the polypeptide; and b) recovering the polypeptidefrom the host cell culture.

The invention also provides a pharmaceutical composition comprising asubstantially purified AFB1 -hAR having the amino acid sequence of SEQID NO:1 in conjunction with a suitable pharmaceutical carrier.

The invention also provides a purified antagonist of the polypeptide ofSEQ ID NO:1. In one aspect the invention provides a purified antibodywhich binds to a polypeptide comprising the amino acid sequence of SEQID NO:1.

Still further, the invention provides a purified agonist of thepolypeptide of SEQ ID NO:1.

The invention also provides a method for treating or preventing agastrointestinal disorder comprising administering to a subject in needof such treatment an effective amount of a pharmaceutical compositioncomprising purified AFB1-hAR.

The invention also provides a method for treating or preventing aneoplastic disorder comprising administering to a subject in need ofsuch treatment an effective amount of a pharmaceutical compositioncomprising purified AFB1-hAR.

The invention also provides a method for detecting a polynucleotidewhich encodes AFB1-hAR in a biological sample comprising the steps of:a) hybridizing the complement of the polynucleotide sequence whichencodes SEQ ID NO:1 to nucleic acid material of a biological sample,thereby forming a hybridization complex; and b) detecting thehybridization complex, wherein the presence of the complex correlateswith the presence of a polynucleotide encoding AFB1-hAR in thebiological sample. In one aspect the nucleic acid material of thebiological sample is amplified by the polymerase chain reaction prior tohybridization.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A, 1B, 1C, and 1D show the amino acid sequence (SEQ ID NO:1) andnucleic acid sequence (SEQ ID NO:2) of AFB1-hAR. The alignment wasproduced using MACDNASIS PRO software (itachi Software Engineering Co.Ltd. San Bruno, Calif.).

FIGS. 2A and 2B show the amino acid sequence alignments between AFB1-hAR(1596452; SEQ ID NO:1) and AFB1-AR from rat liver (GI 433611; SEQ IDNO:3), produced using the multisequence alignment program of DNASTAR™software (DNASTAR Inc, Madison Wis.).

FIGS. 3A and 3B show the hydrophobicity plots for AFB1-hAR (SEQ ID NO:1)and rat liver AFB1-AR (SEQ ID NO:3), respectively; the positive X axisreflects amino acid position, and the negative Y axis, hydrophobicity(MACDNASIS PRO software).

DESCRIPTION OF THE INVENTION

Before the present proteins, nucleotide sequences, and methods aredescribed, it is understood that this invention is not limited to theparticular methodology, protocols, cell lines, vectors, and reagentsdescribed, as these may vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to limit the scope of the presentinvention which will be limited only by the appended claims.

It must be noted that as used herein and in the appended claims, thesingular forms "a", "an", and "the" include plural reference unless thecontext clearly dictates otherwise. Thus, for example, reference to "ahost cell" includes a plurality of such host cells, reference to the"antibody" is a reference to one or more antibodies and equivalentsthereof known to those skilled in the art, and so forth.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methods,devices, and materials are now described. All publications mentionedherein are incorporated herein by reference for the purpose ofdescribing and disclosing the cell lines, vectors, and methodologieswhich are reported in the publications which might be used in connectionwith the invention. Nothing herein is to be construed as an admissionthat the invention is not entitled to antedate such disclosure by virtueof prior invention.

Definitions

AFB1-hAR, as used herein, refers to the amino acid sequences ofsubstantially purified AFB1-hAR obtained from any species, particularlymammalian, including bovine, ovine, porcine, murine, equine, andpreferably human, from any source whether natural, synthetic,semi-synthetic, or recombinant.

The term "agonist", as used herein, refers to a molecule which, whenbound to AFB1-hAR, increases or prolongs the duration of the effect ofAFB1-hAR. Agonists may include proteins, nucleic acids, carbohydrates,or any other molecules which bind to and modulate the effect ofAFB1-hAR.

An "allele" or "allelic sequence", as used herein, is an alternativeform of the gene encoding AFB1-hAR. Alleles may result from at least onemutation in the nucleic acid sequence and may result in altered mRNAs orpolypeptides whose structure or function may or may not be altered. Anygiven natural or recombinant gene may have none, one, or many allelicforms. Common mutational changes which give rise to alleles aregenerally ascribed to natural deletions, additions, or substitutions ofnucleotides. Each of these types of changes may occur alone, or incombination with the others, one or more times in a given sequence.

"Altered" nucleic acid sequences encoding AFB1-hAR as used hereininclude those with deletions, insertions, or substitutions of differentnucleotides resulting in a polynucleotide that encodes the same or afunctionally equivalent AFB1-hAR. Included within this definition arepolymorphisms which may or may not be readily detectable using aparticular oligonucleotide probe of the polynucleotide encodingAFB1-hAR, and improper or unexpected hybridization to alleles, with alocus other than the normal chromosomal locus for the polynucleotidesequence encoding AFB1-hAR. The encoded protein may also be "altered"and contain deletions, insertions, or substitutions of amino acidresidues which produce a silent change and result in a functionallyequivalent AFB1-hAR. Deliberate amino acid substitutions may be made onthe basis of similarity in polarity, charge, solubility, hydrophobicity,hydrophilicity, and/or the amphipathic nature of the residues as long asthe biological or immunological activity of AFB1-hAR is retained. Forexample, negatively charged amino acids may include aspartic acid andglutamic acid; positively charged amino acids may include lysine andarginine; and amino acids with uncharged polar head groups havingsimilar hydrophilicity values may include leucine, isoleucine, andvaline, glycine and alanine, asparagine and glutamine, serine andthreonine, and phenylalanine and tyrosine.

"Amino acid sequence" as used herein refers to an oligopeptide, peptide,polypeptide, or protein sequence, and fragment thereof, and to naturallyoccurring or synthetic molecules. Fragments of AFB1-hAR are preferablyabout 5 to about 15 amino acids in length and retain the biologicalactivity or the immunological activity of AFB1-hAR. Where "amino acidsequence" is recited herein to refer to an amino acid sequence of anaturally occurring protein molecule, amino acid sequence, and liketerms, are not meant to limit the amino acid sequence to the complete,native amino acid sequence associated with the recited protein molecule.

"Amplification" as used herein refers to the production of additionalcopies of a nucleic acid sequence and is generally carried out usingpolymerase chain reaction (PCR) technologies well known in the art(Dieffenbach, C. W. and G. S. Dveksler (1995) PCR Primer, a LaboratoryManual, Cold Spring Harbor Press, Plainview, N.Y.).

The term "antagonist" as used herein, refers to a molecule which, whenbound to AFB1-hAR, decreases the amount or the duration of the effect ofthe biological or immunological activity of AFB1-hAR. Antagonists mayinclude proteins, nucleic acids, carbohydrates, antibodies or any othermolecules which decrease the effect of AFB1-hAR.

As used herein, the term "antibody" refers to intact molecules as wellas fragments thereof, such as Fab, F(ab')₂,and Fv, which are capable ofbinding the epitopic determinant. Antibodies that bind AFB1-hARpolypeptides can be prepared using intact polypeptides or fragmentscontaining small peptides of interest as the immunizing antigen. Thepolypeptide or oligopeptide used to immunize an animal can be derivedfrom the translation of RNA or synthesized chemically and can beconjugated to a carrier protein, if desired. Commonly used carriers thatare chemically coupled to peptides include bovine serum albumin andthyroglobulin, keyhole limpet hemocyanin. The coupled peptide is thenused to immunize the animal (e.g., a mouse, a rat, or a rabbit).

The term "antigenic determinant", as used herein, refers to thatfragment of a molecule (i.e., an epitope) that makes contact with aparticular antibody. When a protein or fragment of a protein is used toimmunize a host animal, numerous regions of the protein may induce theproduction of antibodies which bind specifically to a given region orthree-dimensional structure on the protein; these regions or structuresare referred to as antigenic determinants. An antigenic determinant maycompete with the intact antigen (i.e., the immunogen used to elicit theimmune response) for binding to an antibody.

The term "antisense", as used herein, refers to any compositioncontaining nucleotide sequences which are complementary to a specificDNA or RNA sequence. The term "antisense strand" is used in reference toa nucleic acid strand that is complementary to the "sense" strand.Antisense molecules include peptide nucleic acids and may be produced byany method including synthesis or transcription. Once introduced into acell, the complementary nucleotides combine with natural sequencesproduced by the cell to form duplexes and block either transcription ortranslation. The designation "negative" is sometimes used in referenceto the antisense strand, and "positive" is sometimes used in referenceto the sense strand.

The term "biologically active", as used herein, refers to a proteinhaving structural, regulatory, or biochemical functions of a naturallyoccurring molecule. Likewise, "immunologically active" refers to thecapability of the natural, recombinant, or synthetic AFB1-hAR, or anyoligopeptide thereof, to induce a specific immune response inappropriate animals or cells and to bind with specific antibodies.

The terms "complementary" or "complementarity", as used herein, refer tothe natural binding of polynucleotides under permissive salt andtemperature conditions by base-pairing. For example, the sequence"A-G-T" binds to the complementary sequence "T-C-A". Complementaritybetween two single-stranded molecules may be "partial", in which onlysome of the nucleic acids bind, or it may be complete when totalcomplementarity exists between the single stranded molecules. The degreeof complementarity between nucleic acid strands has significant effectson the efficiency and strength of hybridization between nucleic acidstrands. This is of particular importance in amplification reactions,which depend upon binding between nucleic acids strands and in thedesign and use of PNA molecules.

A "composition comprising a given polynucleotide sequence" as usedherein refers broadly to any composition containing the givenpolynucleotide sequence. The composition may comprise a dry formulationor an aqueous solution. Compositions comprising polynucleotide sequencesencoding AFB1-hAR (SEQ ID NO:1) or fragments thereof (e.g., SEQ ID NO:2and fragments thereof)-may be employed as hybridization probes. Theprobes may be stored in freeze-dried form and may be associated with astabilizing agent such as a carbohydrate. In hybridizations, the probemay be deployed in an aqueous solution containing salts (e.g., NaCl),detergents (e.g., SDS) and other components (e.g., Denhardt's solution,dry milk, salmon sperm DNA, etc.).

"Consensus", as used herein, refers to a nucleic acid sequence which hasbeen resequenced to resolve uncalled bases, has been extended usingXL-PCR extension kit (Perkin Elmer, Norwalk, Conn.) in the 5' and/or the3' direction and resequenced, or has been assembled from the overlappingsequences of more than one Incyte Clone using a computer program forfragment assembly (e.g., GELVIEW fragment assembly system, GCG, Madison,Wis.). Some sequences have been both extended and assembled to producethe consensus sequence.

The term "correlates with expression of a polynucleotide", as usedherein, indicates that the detection of the presence of ribonucleic acidthat is similar to SEQ ID NO:2 by northern analysis is indicative of thepresence of mRNA encoding AFB1-hAR in a sample and thereby correlateswith expression of the transcript from the polynucleotide encoding theprotein.

A "deletion", as used herein, refers to a change in the amino acid ornucleotide sequence and results in the absence of one or more amino acidresidues or nucleotides.

The term "derivative", as used herein, refers to the chemicalmodification of a nucleic acid encoding or complementary to AFB1-hAR orthe encoded AFB1-hAR. Such modifications include, for example,replacement of hydrogen by an alkyl, acyl, or amino group. A nucleicacid derivative encodes a polypeptide which retains the biological orimmunological function of the natural molecule. A derivative polypeptideis one which is modified by glycosylation, pegylation, or any similarprocess which retains the biological or immunological function of thepolypeptide from which it was derived.

The term "homology", as used herein, refers to a degree ofcomplementarity. There may be partial homology or complete homology(i.e., identity). A partially complementary sequence that at leastpartially inhibits an identical sequence from hybridizing to a targetnucleic acid is referred to using the functional term "substantiallyhomologous." The inhibition of hybridization of the completelycomplementary sequence to the target sequence may be examined using ahybridization assay (Southern or northern blot, solution hybridizationand the like) under conditions of low stringency. A substantiallyhomologous sequence or hybridization probe will compete for and inhibitthe binding of a completely homologous sequence to the target sequenceunder conditions of low stringency. This is not to say that conditionsof low stringency are such that non-specific binding is permitted; lowstringency conditions require that the binding of two sequences to oneanother be a specific (i.e., selective) interaction. The absence ofnon-specific binding may be tested by the use of a second targetsequence which lacks even a partial degree of complementarity (e.g.,less than about 30% identity). In the absence of non-specific binding,the probe will not hybridize to the second non-complementary targetsequence.

Human artificial chromosomes (HACs) are linear microchromosomes whichmay contain DNA sequences of 10K to 10M in size and contain all of theelements required for stable mitotic chromosome segregation andmaintenance (Harrington, J. J. et al. (1997) Nat Genet. 15:345-355).

The term "humanized antibody", as used herein, refers to antibodymolecules in which amino acids have been replaced in the non-antigenbinding regions in order to more closely resemble a human antibody,while still retaining the original binding ability.

The term "hybridization", as used herein, refers to any process by whicha strand of nucleic acid binds with a complementary strand through basepairing.

The term "hybridization complex", as used herein, refers to a complexformed between two nucleic acid sequences by virtue of the formation ofhydrogen bonds between complementary G and C bases and betweencomplementary A and T bases; these hydrogen bonds may be furtherstabilized by base stacking interactions. The two complementary nucleicacid sequences hydrogen bond in an antiparallel configuration. Ahybridization complex may be formed in solution (e.g., C₀ t or R₀ tanalysis) or between one nucleic acid sequence present in solution andanother nucleic acid sequence immobilized on a solid support (e.g.,paper, membranes, filters, chips, pins or glass slides, or any otherappropriate substrate to which cells or their nucleic acids have beenfixed).

An "insertion" or "addition", as used herein, refers to a change in anamino acid or nucleotide sequence resulting in the addition of one ormore amino acid residues or nucleotides, respectively, as compared tothe naturally occurring molecule.

"Microarray" refers to an array of distinct polynucleotides oroligonucleotides synthesized on a substrate, such as paper, nylon orother type of membrane, filter, chip, glass slide, or any other suitablesolid support.

The term "modulate", as used herein, refers to a change in the activityof AFB1-hAR. For example, modulation may cause an increase or a decreasein protein activity, binding characteristics, or any other biological,functional or immunological properties of AFB1-hAR.

"Nucleic acid sequence" as used herein refers to an oligonucleotide,nucleotide, or polynucleotide, and fragments thereof, and to DNA or RNAof genomic or synthetic origin which may be single- or double-stranded,and represent the sense or antisense strand. "Fragments" are thosenucleic acid sequences which are greater than 60 nucleotides than inlength, and most preferably includes fragments that are at least 100nucleotides or at least 1000 nucleotides, and at least 10,000nucleotides in length.

The term "oligonucleotide" refers to a nucleic acid sequence of at leastabout 6 nucleotides to about 60 nucleotides, preferably about 15 to 30nucleotides, and more preferably about 20 to 25 nucleotides, which canbe used in PCR amplification or a hybridization assay, or a microarray.As used herein, oligonucleotide is substantially equivalent to the terms"amplimers", "primers", "oligomers", and "probes", as commonly definedin the art.

"Peptide nucleic acid", PNA as used herein, refers to an antisensemolecule or anti-gene agent which comprises an oligonucleotide of atleast five nucleotides in length linked to a peptide backbone of aminoacid residues which ends in lysine. The terminal lysine conferssolubility to the composition. PNAs may be pegylated to extend theirlifespan in the cell where they preferentially bind complementary singlestranded DNA and RNA and stop transcript elongation (Nielsen, P. E. etal. (1993) Anticancer Drug Des. 8: 3-63).

The term "portion", as used herein, with regard to a protein (as in "aportion of a given protein") refers to fragments of that protein. Thefragments may range in size from five amino acid residues to the entireamino acid sequence minus one amino acid. Thus, a protein "comprising atleast a portion of the amino acid sequence of SEQ ID NO:1" encompassesthe full-length AFB1-hAR and fragments-thereof.

The term "sample", as used herein, is used in its broadest sense. Abiological sample suspected of containing nucleic acid encodingAFB1-hAR, or fragments thereof, or AFB1-hAR itself may comprise a bodilyfluid, extract from a cell, chromosome, organelle, or membrane isolatedfrom a cell, a cell, genomic DNA, RNA, or DNA (in solution or bound to asolid support, a tissue, a tissue print, and the like).

The terms "specific binding" or "specifically binding", as used herein,refers to that interaction between a protein or peptide and an agonist,an antibody and an antagonist. The interaction is dependent upon thepresence of a particular structure (i.e., the antigenic determinant orepitope) of the protein recognized by the binding molecule. For example,if an antibody is specific for epitope "A", the presence of a proteincontaining epitope A (or free, unlabeled A) in a reaction containinglabeled "A" and the antibody will reduce the amount of labeled A boundto the antibody.

The terms "stringent conditions" or "stringency", as used herein, referto the conditions for hybridization as defined by the nucleic acid,salt, and temperature. These conditions are well known in the art andmay be altered in order to identify or detect identical or relatedpolynucleotide sequences. Numerous equivalent conditions comprisingeither low or high stringency depend on factors such as the length andnature of the sequence (DNA, RNA, base composition), nature of thetarget (DNA, RNA, base composition), milieu (in solution or immobilizedon a solid substrate), concentration of salts and other components is(e.g., formamide, dextran sulfate and/or polyethylene glycol), andtemperature of the reactions (within a range from about 5° C. below themelting temperature of the probe to about 20° C. to 25° C. below themelting temperature). One or more factors be may be varied to generateconditions of either low or high stringency different from, butequivalent to, the above listed conditions.

The term "substantially purified", as used herein, refers to nucleic oramino acid sequences that are removed from their natural environment,isolated or separated, and are at least 60% free, preferably 75% free,and most preferably 90% free from other components with which they arenaturally associated.

A "substitution", as used herein, refers to the replacement of one ormore amino acids or nucleotides by different amino acids or nucleotides,respectively.

"Transformation", as defined herein, describes a process by whichexogenous DNA enters and changes a recipient cell. It may occur undernatural or artificial conditions using various methods well known in theart. Transformation may rely on any known method for the insertion offoreign nucleic acid sequences into a prokaryotic or eukaryotic hostcell. The method is selected based on the type of host cell beingtransformed and may include, but is not limited to, viral infection,electroporation, heat shock, lipofection, and particle bombardment. Such"transformed" cells include stably transformed cells in which theinserted DNA is capable of replication either as an autonomouslyreplicating plasmid or as part of the host chromosome. They also includecells which transiently express the inserted DNA or RNA for limitedperiods of time.

A "variant" of AFB1-hAR, as used herein, refers to an amino acidsequence that is altered by one or more amino acids. The variant mayhave "conservative" changes, wherein a substituted amino acid hassimilar structural or chemical properties, e.g., replacement of leucinewith isoleucine. More rarely, a variant may have "nonconservative"changes, e.g., replacement of a glycine with a tryptophan. Analogousminor variations may also include amino acid deletions or insertions, orboth. Guidance in determining which amino acid residues may besubstituted, inserted, or deleted without abolishing biological orimmunological activity may be found using computer programs well knownin the art, for example, DNASTAR software.

The Invention

The invention is based on the discovery of a new human aflatoxin B1aldehyde reductase (hereinafter referred to as "AFB1-hAR"), thepolynucleotides encoding AFB1-hAR, and the use of these compositions forthe diagnosis, prevention, or treatment of gastrointestinal andneoplastic disorders.

Nucleic acids encoding the AFB1-hAR of the present invention were firstidentified in Incyte Clone 1596452 from the astrocytoma-associated braintissue cDNA library BRAINOT14 using a computer search for amino acidsequence alignments. A consensus sequence, SEQ ID NO:2, was derived fromthe following overlapping and/or extended nucleic acid sequences: IncyteClones 887238 (PANCNOT05), 1623504 (BRAITUT13), 1630438 (COLNNOT19),1594652 (BRAINOT14), 1312614 (BLADTUT02), and 2350042 (COLSUCT01).

In one embodiment, the invention encompasses a polypeptide comprisingthe amino acid sequence of SEQ ID NO:1, as shown in FIGS. 1A, 1B, 1C,and 1D. AFB1-hAR is 331 amino acids in length and, as shown in FIGS. 2Aand 2B, has chemical and structural homology with rat liver AFB1-AR (GI433611; SEQ ID NO:3). In particular, AFB1-hAR and rat liver AFB1-ARshare 80% amino acid sequence identity. The putative active site His109of rat AFB1-AR aligns with His113 of AFB1-hAR. As illustrated by FIGS.3A and 3B, AFB1-hAR and rat liver AFB1-AR have similar hydrophobicityplots. Northern analysis shows the expression of AFB1-hAR in variouslibraries, including liver, colon, large intestine, small intestine,stomach, olfactory epithelium, brain, prostate, bladder, lung, heart,thyroid, parathyroid, ovary, kidney, and penis; epithelial cell linesfrom colon, nasal mucosa, and lung; fetal colon, placenta, lung, kidney,liver, and spleen. Of particular note is the expression of AFB1-hAR indisorders of the gastrointestinal system, including irritable bowelsyndrome, ulcerative colitis, Crohn's disease, and cholecystitis; and inneoplastic disorders including tumors, polyps, and hyperplasia of theliver, colon, nasal cavity, prostate, bladder, thyroid, ovary,parathyroid, penis, and kidney. The similarity of AFB1-hAR to rat liverAFB1-AR and its association with disorders of the gastrointestinal tractand neoplastic disorders suggest that AFB1-hAR plays a role in thedetoxification of AFB1 and related compounds. Furthermore, AFB1-hAR maybe subject to transcriptional regulation by inducers such as ethoxyquinin a manner similar to rat AFB1-AR.

The invention also encompasses AFB1-hAR variants. A preferred AFB1-hARvariant is one having at least 80%, and more preferably at least 90%,amino acid sequence identity to the AFB1-hAR amino acid sequence (SEQ IDNO:1) and which retains at least one biological, immunological or otherfunctional characteristic or activity of AFB1-hAR. A most preferredAFB1-hAR variant is one having at least 95% amino acid sequence identityto SEQ ID NO:1.

The invention also encompasses polynucleotides which encode AFB1-hAR.Accordingly, any nucleic acid sequence which encodes the amino acidsequence of AFB1-hAR can be used to produce recombinant molecules whichexpress AFB1-hAR. In a particular embodiment, the invention encompassesthe polynucleotide comprising the nucleic acid sequence of SEQ ID NO:2as shown in FIGS. 1A, 1B, 1C, and 1D.

It will be appreciated by those skilled in the art that as a result ofthe degeneracy of the genetic code, a multitude of nucleotide sequencesencoding AFB1-hAR, some bearing minimal homology to the nucleotidesequences of any known and naturally occurring gene, may be produced.Thus, the invention contemplates each and every possible variation ofnucleotide sequence that could be made by selecting combinations basedon possible codon choices. These combinations are made in accordancewith the standard triplet genetic code as applied to the nucleotidesequence of naturally occurring AFB1-hAR, and all such variations are tobe considered as being specifically disclosed.

Although nucleotide sequences which encode AFB1-hAR and its variants arepreferably capable of hybridizing to the nucleotide sequence of thenaturally occurring AFB1-hAR under appropriately selected conditions ofstringency, it may be advantageous to produce nucleotide sequencesencoding AFB1-hAR or its derivatives possessing a substantiallydifferent codon usage. Codons may be selected to increase the rate atwhich expression of the peptide occurs in a particular prokaryotic oreukaryotic host in accordance with the frequency with which particularcodons are utilized by the host. Other reasons for substantiallyaltering the nucleotide sequence encoding AFB1-hAR and its derivativeswithout altering the encoded amino acid sequences include the productionof RNA transcripts having more desirable properties, such as a greaterhalf-life, than transcripts produced from the naturally occurringsequence.

The invention also encompasses production of DNA sequences, or fragmentsthereof, which encode AFB1-hAR and its derivatives, entirely bysynthetic chemistry. After production, the synthetic sequence may beinserted into any of the many available expression vectors and cellsystems using reagents that are well known in the art. Moreover,synthetic chemistry may be used to introduce mutations into a sequenceencoding AFB1-hAR or any fragment thereof.

Also encompassed by the invention are polynucleotide sequences that arecapable of hybridizing to the claimed nucleotide sequences, and inparticular, those shown in SEQ ID NO:2, under-various conditions ofstringency as taught in Wahl, G. M. and S. L. Berger (1987; MethodsEnzymol. 152:399-407) and Kimmel, A. R. (1987; Methods Enzymol.152:507-511).

Methods for DNA sequencing which are well known and generally availablein the art and may be used to practice any of the embodiments of theinvention. The methods may employ such enzymes as the Klenow fragment ofDNA polymerase I, SEQUENASE DNA polymerase (US Biochemical Corp,Cleveland, Ohio), Taq polymerase (Perkin Elmer), thermostable T7polymerase (Amersham, Chicago, Ill.), or combinations of polymerases andproofreading exonucleases such as those found in the ELONGASEamplification system marketed by Gibco/BRL (Gaithersburg, Md.).Preferably, the process is automated with machines such as the HamiltonMICROLAB 2200 (Hamilton, Reno, Nev.), Peltier thermal cycler (PTC200; MJResearch, Watertown, Mass.) and the ABI CATALYST and 373 and 377 DNAsequencers (Perkin Elmer).

The nucleic acid sequences encoding AFB1-hAR may be extended utilizing apartial nucleotide sequence and employing various methods known in theart to detect upstream sequences such as promoters and regulatoryelements. For example, one method which may be employed,"restriction-site" PCR, uses universal primers to retrieve unknownsequence adjacent to a known locus (Sarkar, G. (1993) PCR MethodsApplic. 2:318-322). In particular, genomic DNA is first amplified in thepresence of primer to a linker sequence and a primer specific to theknown region. The amplified sequences are then subjected to a secondround of PCR with the same linker primer and another specific primerinternal to the first one. Products of each round of PCR are transcribedwith an appropriate RNA polymerase and sequenced using reversetranscriptase.

Inverse PCR may also be used to amplify or extend sequences usingdivergent primers based on a known region (Triglia, T. et al. (1988)Nucleic Acids Res. 16:8186). The primers may be designed usingcommercially available software such as OLIGO 4.06 primer analysissoftware (National Biosciences Inc., Plymouth, Minn.), or anotherappropriate program, to be 22-30 nucleotides in length, to have a GCcontent of 50% or more, and to anneal to the target sequence attemperatures about 68°-72° C. The method uses several restrictionenzymes to generate a suitable fragment in the known region of a gene.The fragment is then circularized by intramolecular ligation and used asa PCR template.

Another method which may be used is capture PCR which involves PCRamplification of DNA fragments adjacent to a known sequence in human andyeast artificial chromosome DNA (Lagerstrom, M. et al. (1991) PCRMethods Applic. 1:111-119). In this method, multiple restriction enzymedigestions and ligations may also be used to place an engineereddouble-stranded sequence into an unknown fragment of the DNA moleculebefore performing PCR.

Another method which may be used to retrieve unknown sequences is thatof Parker, J. D. et al. (1991; Nucleic Acids Res. 19:3055-3060).Additionally, one may use PCR, nested primers, and PROMOTERFINDERlibraries to walk genomic DNA (Clontech, Palo Alto, Calif.). Thisprocess avoids the need to screen libraries and is useful in findingintron/exon junctions.

When screening for full-length cDNAs, it is preferable to use librariesthat have been size-selected to include larger cDNAs. Also,random-primed libraries are preferable, in that they will contain moresequences which contain the 5' regions of genes. Use of a randomlyprimed library may be especially preferable for situations in which anoligo d(T) library does not yield a full-length cDNA. Genomic librariesmay be useful for extension of sequence into 5' non-transcribedregulatory regions.

Capillary electrophoresis systems which are commercially available maybe used to analyze the size or confirm the nucleotide sequence ofsequencing or PCR products. In particular, capillary sequencing mayemploy flowable polymers for electrophoretic separation, four differentfluorescent dyes (one for each nucleotide) which are laser activated,and detection of the emitted wavelengths by a charge coupled devisecamera. Output/light intensity may be converted to electrical signalusing appropriate software (e.g. GENOTYPER and SEQUENCE NAVIGATORsoftware, Perkin Elmer) and the entire process from loading of samplesto computer analysis and electronic data display may be computercontrolled. Capillary electrophoresis is especially preferable for thesequencing of small pieces of DNA which might be present in limitedamounts in a particular sample.

In another embodiment of the invention, polynucleotide sequences orfragments thereof which encode AFB1-hAR may be used in recombinant DNAmolecules to direct expression of AFB1-hAR, fragments or functionalequivalents thereof, in appropriate host cells. Due to the inherentdegeneracy-of the genetic code, other DNA sequences which encodesubstantially the same or a functionally equivalent amino acid sequencemay be produced, and these sequences may be used to clone and expressAFB1-hAR.

As will be understood by those of skill in the art, it may beadvantageous to produce AFB1-hAR-encoding nucleotide sequencespossessing non-naturally occurring codons. For example, codons preferredby a particular prokaryotic or eukaryotic host can be selected toincrease the rate of protein expression or to produce an RNA transcripthaving desirable properties, such as a half-life which is longer thanthat of a transcript generated from the naturally occurring sequence.

The nucleotide sequences of the present invention can be engineeredusing methods generally known in the art in order to alter AFB1-hARencoding sequences for a variety of reasons, including but not limitedto, alterations which modify the cloning, processing, and/or expressionof the gene product. DNA shuffling by random fragmentation and PCRreassembly of gene fragments and synthetic oligonucleotides may be usedto engineer the nucleotide sequences. For example, site-directedmutagenesis may be used to insert new restriction sites, alterglycosylation patterns, change codon preference, produce splicevariants, introduce mutations, and so forth.

In another embodiment of the invention, natural, modified, orrecombinant nucleic acid sequences encoding AFB1-hAR may be ligated to aheterologous sequence to encode a fusion protein. For example, to screenpeptide libraries for inhibitors of AFB1-hAR activity, it may be usefulto encode a chimeric AFB1-hAR protein that can be recognized by acommercially available antibody. A fusion protein may also be engineeredto contain a cleavage site located between the AFB1-hAR encodingsequence and the heterologous protein sequence, so that AFB1-hAR may becleaved and purified away from the heterologous moiety.

In another embodiment, sequences encoding AFB1-hAR may be synthesized,in whole or in part, using chemical methods well known in the art (seeCaruthers, M. H. et al. (1980) Nucl. Acids Res. Symp. Ser. 7:215-223,Horn, T. et at (1980) Nucl. Acids Res. Symp. Ser. 7:225-232).Alternatively, the protein itself may be produced using chemical methodsto synthesize the amino acid sequence of AFB1-hAR, or a fragmentthereof. For example, peptide synthesis can be performed using varioussolid-phase techniques (Roberge, J. Y. et al. (1995) Science269:202-204) and automated synthesis may be achieved, for example, usingthe ABI 431 A peptide synthesizer (Perkin Elmer).

The newly synthesized peptide may be substantially purified bypreparative high performance liquid chromatography (e.g., Creighton, T.(1983) Proteins, Structures and Molecular Principles, W H Freeman andCo., New York, N.Y.). The composition of the synthetic peptides may beconfirmed by amino acid analysis or sequencing (e.g., the Edmandegradation procedure; Creighton, supra). Additionally, the amino acidsequence of AFB1-hAR, or any part thereof, may be altered during directsynthesis and/or combined using chemical methods with sequences fromother proteins, or any part thereof, to produce a variant polypeptide.

In order to express a biologically active AFB1-hAR, the nucleotidesequences encoding AFB1-hAR or functional equivalents, may be insertedinto appropriate expression vector, i.e., a vector which contains thenecessary elements for the transcription and translation of the insertedcoding sequence.

Methods which are well known to those skilled in the art may be used toconstruct expression vectors containing sequences encoding AFB1-hAR andappropriate transcriptional and translational control elements. Thesemethods include in vitro recombinant DNA techniques, synthetictechniques, and in vivo genetic recombination. Such techniques aredescribed in Sambrook, J. et al. (1989) Molecular Cloning, A LaboratoryManual, Cold Spring Harbor Press, Plainview, N.Y., and Ausubel, F. M. etal. (1989) Current Protocols in Molecular Biology, John Wiley & Sons,New York, N.Y.

A variety of expression vector/host systems may be utilized to containand express sequences encoding AFB1-hAR. These include, but are notlimited to, microorganisms such as bacteria transformed with recombinantbacteriophage, plasmid, or cosmid DNA expression vectors; yeasttransformed with yeast expression vectors; insect cell systems infectedwith virus expression vectors (e.g., baculovirus); plant cell systemstransformed with virus expression vectors (e.g., cauliflower mosaicvirus, CaMV; tobacco mosaic virus, TMV) or with bacterial expressionvectors (e.g., Ti or pBR322 plasmids); or animal cell systems. Theinvention is not limited by the host cell employed.

The "control elements" or "regulatory sequences" are thosenon-translated regions of the vector--enhancers, promoters, 5' and 3'untranslated regions--which interact with host cellular proteins tocarry out transcription and translation. Such elements may vary in theirstrength and specificity. Depending on the vector system and hostutilized, any number of suitable transcription and translation elements,including constitutive and inducible promoters, may be used. Forexample, when cloning in bacterial systems, inducible promoters such asthe hybrid lacZ promoter of the BLUESCRIPT phagemid (Stratagene,LaJolla, Calif.) or PSPORT1 plasmid (Gibco BRL) and the like may beused. The baculovirus polyhedrin promoter may be used in insect cells.Promoters or enhancers derived from the genomes of plant cells (e.g.,heat shock, RUBISCO; and storage protein genes) or from plant viruses(e.g., viral promoters or leader sequences) may be cloned into thevector. In mammalian cell systems, promoters from mammalian genes orfrom mammalian viruses are preferable. If it is necessary to generate acell line that contains multiple copies of the sequence encodingAFB1-hAR, vectors based on SV40 or EBV may be used with an appropriateselectable marker.

In bacterial systems, a number of expression vectors may be selecteddepending upon the use intended for AFB1-hAR. For example, when largequantities of AFB1-hAR are needed for the induction of antibodies,vectors which direct high level expression of fusion proteins that arereadily purified may be used. Such vectors include, but are not limitedto, the multifunctional E. coli cloning and expression vectors such asBluescript® (Stratagene), in which the sequence encoding AFB1-hAR may beligated into the vector in frame with sequences for the amino-terminalMet and the subsequent 7 residues of β-galactosidase so that a hybridprotein is produced; pIN vectors (Van Heeke, G. and S. M. Schuster(1989) J. Biol. Chem. 264:5503-5509); and the like. PGEX vectors(Promega, Madison, Wis.) may also be used to express foreignpolypeptides as fusion proteins with glutathione S-transferase (GST). Ingeneral, such fusion proteins are soluble and can easily be purifiedfrom lysed cells by adsorption to glutathione-agarose beads followed byelution in the presence of free glutathione. Proteins made in suchsystems may be designed to include heparin, thrombin, or factor XAprotease cleavage sites so that the cloned polypeptide of interest canbe released from the GST moiety at will.

In the yeast, Saccharomyces cerevisiae, a number of vectors containingconstitutive or inducible promoters such as alpha factor, alcoholoxidase, and PGH may be used. For reviews, see Ausubel et al. (supra)and Grant et al. (1987) Methods Enzymol. 153:516-544.

In cases where plant expression vectors are used, the expression ofsequences encoding AFB1-hAR may be driven by any of a number ofpromoters. For example, viral promoters such as the 35S and 19Spromoters of CaMV may be used alone or in combination with the omegaleader sequence from TMV (Takamatsu, N. (1987) EMBO J. 6:307-311).Alternatively, plant promoters such as the small subunit of RUBISCO orheat shock promoters may be used (Coruzzi, G. et al. (1984) EMBO J.3:1671-1680; Broglie, R. et al. (1984) Science 224:838-843; and Winter,J. et al. (1991) Results Probl. Cell Differ. 17:85-105). Theseconstructs can be introduced into plant cells by direct DNAtransformation or pathogen-mediated transfection. Such techniques aredescribed in a number of generally available reviews (see, for example,Hobbs, S. or Murry, L. E. in McGraw Hill Yearbook of Science adTechnology (1992) McGraw Hill, New York, N.Y.; pp. 191-196.

An insect system may also be used to express AFB1-hAR. For example, inone such system, Autographa californica nuclear polyhedrosis virus(AcNPV) is used as a vector to express foreign genes in Spodopterafrugiperda cells or in Trichoplusia larvae. The sequences encodingAFB1-hAR may be cloned into a non-essential region of the virus, such asthe polyhedrin gene, and placed under control of the polyhedrinpromoter. Successful insertion of AFB1-hAR will render the polyhedringene inactive and produce recombinant virus lacking coat protein. Therecombinant viruses may then be used to infect, for example, S.frugiperda cells or Trichoplusia larvae in which AFB1-hAR may beexpressed (Engelhard, E. K. et al. (1994) Proc. Nat. Acad. Sci.91:3224-3227).

In mammalian host cells, a number of viral-based expression systems maybe utilized. In cases where an adenovirus is used as an expressionvector, sequences encoding AFB1-hAR may be ligated into an adenovirustranscription/translation complex consisting of the late promoter andtripartite leader sequence. Insertion in a non-essential E1 or E3 regionof the viral genome may be used to obtain a viable virus which iscapable of expressing AFB1-hAR in infected host cells (Logan, J. andShenk, T. (1984) Proc. Natl. Acad. Sci. 81:3655-3659). In addition,transcription enhancers, such as the Rous sarcoma virus (RSV) enhancer,may be used to increase expression in mammalian host cells.

Human artificial chromosomes (HACs) may also be employed to deliverlarger fragments of DNA than can be contained and expressed in aplasmid. HACs of 6 to 10M are constructed and delivered via conventionaldelivery methods (liposomes, polycationic amino polymers, or vesicles)for therapeutic purposes.

Specific initiation signals may also be used to achieve more efficienttranslation of sequences encoding AFB1-hAR. Such signals include the ATGinitiation codon and adjacent sequences. In cases where sequencesencoding AFB1-hAR, its initiation codon, and upstream sequences areinserted into the appropriate expression vector, no additionaltranscriptional or translational control signals may be needed. However,in cases where only coding sequence, or a fragment thereof, is inserted,exogenous translational control signals including the ATG initiationcodon should be provided. Furthermore, the initiation codon should be inthe correct reading frame to ensure translation of the entire insert.Exogenous translational elements and initiation codons may be of variousorigins, both natural and synthetic. The efficiency of expression may beenhanced by the inclusion of enhancers which are appropriate for theparticular cell system which is used, such as those described in theliterature (Scharf, D. et al. (1994) Results Probl. Cell Differ.20:125-162).

In addition, a host cell strain may be chosen for its ability tomodulate the expression of the inserted sequences or to process theexpressed protein in the desired fashion. Such modifications of thepolypeptide include, but are not limited to, acetylation, carboxylation,glycosylation, phosphorylation, lipidation, and acylation.Post-translational processing which cleaves a "prepro" form of theprotein may also be used to facilitate correct insertion, folding and/orfunction. Different host cells which have specific cellular machineryand characteristic mechanisms for post-translational activities (e.g.,CHO, HeLa, MDCK, HEK293, and WI38), are available from the American TypeCulture Collection (ATCC; Bethesda, Md.) and may be chosen to ensure thecorrect modification and processing of the foreign protein.

For long-term, high-yield production of recombinant proteins, stableexpression is preferred. For example, cell lines which stably expressAFB1-hAR may be transformed using expression vectors which may containviral origins of replication and/or endogenous expression elements and aselectable marker gene on the same or on a separate vector. Followingthe introduction of the vector, cells may be allowed to grow for 1-2days in an enriched media before they are switched to selective media.The purpose of the selectable marker is to confer resistance toselection, and its presence allows growth and recovery of cells whichsuccessfully express the introduced sequences. Resistant clones ofstably transformed cells may be proliferated using tissue culturetechniques appropriate to the cell type.

Any number of selection systems may be used to recover transformed celllines. These include, but are not limited to, the herpes simplex virusthymidine kinase (Wigler, M. et al. (1977) Cell 11:223-32) and adeninephosphoribosyltransferase (Lowy, I. et al. (1980) Cell 22:817-23) geneswhich can be employed in tk⁻ or aprt⁻ cells, respectively. Also,antimetabolite, antibiotic or herbicide resistance can be used as thebasis for selection; for example, dhfr which confers resistance tomethotrexate (Wigler, M. et al. (1980) Proc. Natl. Acad. Sci.77:3567-70); npt, which confers resistance to the aminoglycosidesneomycin and G-418 (Colbere-Garapin, F. et al (1981) J. Mol. Biol.150:1-14) and als or pat, which confer resistance to chlorsulfuron andphosphinotricin acetyltransferase, respectively (Murry, supra).Additional selectable genes have been described, for example, trpB,which allows cells to utilize indole in place of tryptophan, or hisD,which allows cells to utilize histinol in place of histidine (Hartman,S. C. and R. C. Mulligan (1988) Proc. Natl. Acad. Sci. 85:8047-51).Recently, the use of visible markers has gained popularity with suchmarkers as anthocyanins, β glucuronidase and its substrate GUS, andluciferase and its substrate luciferin, being widely used not only toidentify transformants, but also to quantify the amount of transient orstable protein expression attributable to a specific vector system(Rhodes, C. A. et al. (1995) Methods Mol. Biol. 55:121-131).

Although the presence/absence of marker gene expression suggests thatthe gene of interest is also present, its presence and expression mayneed to be confirmed. For example, if the sequence encoding AFB1-hAR isinserted within a marker gene sequence, transformed cells containingsequences encoding AFB1-hAR can be identified by the absence of markergene function. Alternatively, a marker gene can be placed in tandem witha sequence encoding AFB1-hAR under the control of a single promoter.Expression of the marker gene in response to induction or selectionusually indicates expression of the tandem gene as well.

Alternatively, host cells which contain the nucleic acid sequenceencoding AFB1-hAR and express AFB1-hAR may be identified by a variety ofprocedures known to those of skill in the art. These procedures include,but are not limited to, DNA--DNA or DNA-RNA hybridizations and proteinbioassay or immunoassay techniques which include membrane, solution, orchip based technologies for the detection and/or quantification ofnucleic acid or protein.

The presence of polynucleotide sequences encoding AFB1-hAR can bedetected by DNA--DNA or DNA-RNA hybridization or amplification usingprobes or fragments or fragments of polynucleotides encoding AFB1-hAR.Nucleic acid amplification based assays involve the use ofoligonucleotides or oligomers based on the sequences encoding AFB1-hARto detect transformants containing DNA or RNA encoding AFB1-hAR.

A variety of protocols for detecting and measuring the expression ofAFB1-hAR, using either polyclonal or monoclonal antibodies specific forthe protein are known in the art. Examples include enzyme-linkedimmunosorbent assay (ELISA), radioimmunoassay (RIA), and fluorescenceactivated cell sorting (FACS). A two-site, monoclonal-based immunoassayutilizing monoclonal antibodies reactive to two non-interfering epitopeson AFB1-hAR is preferred, but a competitive binding assay may beemployed. These and other assays are described, among other places, inHampton, R. et al. (1990; Serological Methods, a Laboratory Manual, APSPress, St Paul, Minn.) and Maddox, D. E. et al. (1983; J. Exp. Med.158:1211-1216).

A wide variety of labels and conjugation techniques are known by thoseskilled in the art and may be used in various nucleic acid and aminoacid assays. Means for producing labeled hybridization or PCR probes fordetecting sequences related to polynucleotides encoding AFB1-hAR includeoligolabeling, nick translation, end-labeling or PCR amplification usinga labeled nucleotide. Alternatively, the sequences encoding AFB1-hAR, orany fragments thereof may be cloned into a vector for the production ofan mRNA probe. Such vectors are known in the art, are commerciallyavailable, and may be used to synthesize RNA probes in vitro by additionof an appropriate RNA polymerase such as T7, T3, or SP6 and labelednucleotides. These procedures may be conducted using a variety ofcommercially available kits (Pharmacia & Upjohn, (Kalamazoo, Mich.);Promega (Madison Wis.); and U.S. Biochemical Corp., Cleveland, Ohio).Suitable reporter molecules or labels, which may be used for ease ofdetection, include radionuclides, enzymes, fluorescent,chemiluminescent, or chromogenic agents as well as substrates,cofactors, inhibitors, magnetic particles, and the like.

Host cells transformed with nucleotide sequences encoding AFB1-hAR maybe cultured under conditions suitable for the expression and recovery ofthe protein from cell culture. The protein produced by a transformedcell may be secreted or contained intracellularly depending on thesequence and/or the vector used. As will be understood by those of skillin the art, expression vectors containing polynucleotides which encodeAFB1-hAR may be designed to contain signal sequences which directsecretion of AFB1-hAR through a prokaryotic or eukaryotic cell membrane.Other constructions may be used to join sequences encoding AFB1-hAR tonucleotide sequence encoding a polypeptide domain which will facilitatepurification of soluble proteins. Such purification facilitating domainsinclude, but are not limited to, metal chelating peptides such ashistidine-tryptophan modules that allow purification on immobilizedmetals, protein A domains that allow purification on immobilizedimmunoglobulin, and the domain utilized in the FLAG extension/affinitypurification system (Immunex Corp., Seattle, Wash.). The inclusion ofcleavable linker sequences such as those specific for Factor XA orenterokinase (Invitrogen, San Diego, Calif.) between the purificationdomain and AFB1-hAR may be used to facilitate purification. One suchexpression vector provides for expression of a fusion protein containingAFB1-hAR and a nucleic acid encoding 6 histidine residues preceding athioredoxin or an enterokinase cleavage site. The histidine residuesfacilitate purification on IMIAC (immobilized metal ion affinitychromatography) as described in Porath, J. et al. (1992, Prot. Exp.Purif. 3: 263-281) while the enterokinase cleavage site provides a meansfor purifying AFB1-hAR from the fusion protein. A discussion of vectorswhich contain fusion proteins is provided in Kroll, D. J. et al. (1993;DNA Cell Biol. 12:441-453).

In addition to recombinant production, fragments of AFB1-hAR may beproduced by direct peptide synthesis using solid-phase techniques(Merrifield J. (1963) J. Am. Chem. Soc. 25 85:2149-2154). Proteinsynthesis may be performed using manual techniques or by automation.Automated synthesis may be achieved, for example, using AppliedBiosystems 431A peptide synthesizer (Perkin Elmer). Various fragments ofAFB1-hAR may be chemically synthesized separately and combined usingchemical methods to produce the full length molecule.

Therapeutics

Chemical and structural homology exists between AFB1-hAR and AFB1-ARfrom rat liver (GI 433611). In addition, AFB1-hAR is expressed ingastrointestinal and neoplastic disorders. Therefore, AFB1-hAR appearsto play a role in the detoxification of AFB1 and related compounds andmay reduce the toxicity and/or carcinogenicity of such compounds.AFB1-hAR is particularly useful for individuals at high risk forhepatoma, liver disease, or other disorders associated with AFB1 due toenvironmental or genetic factors.

Therefore, in one embodiment, AFB1-hAR or a fragment or derivativethereof may be administered to a subject to treat a gastrointestinaldisorder. Such disorders include, but are not limited to, ascites,cholelithiasis, cholecystitis, cirrhosis, Crohn's disease,diverticulitis, fulminant hepatitis, gastritis, gastric and duodenalulcers, hepatorenal syndrome, irritable bowel syndrome, jaundice,pancreatitis, and ulcerative colitis.

In another embodiment, a vector capable of expressing AFB1-hAR, or afragment or a derivative thereof, may also be administered to a subjectto treat a gastrointestinal disorder including, but not limited to,those described above.

In still another embodiment, an agonist which modulates the activity ofAFB1-hAR may also be administered to a subject to treat agastrointestinal disorder including, but not limited to, those describedabove.

In another embodiment, AFB1-hAR or a fragment or derivative thereof maybe administered to a subject to treat a neoplastic disorder. Suchdisorders include, but are not limited to, adenocarcinoma, leukemia,lymphoma, melanoma, myeloma, sarcoma, and teratocarcinoma, andparticularly cancers of the adrenal gland, bladder, bone, bone marrow,brain, breast, cervix, gall bladder, ganglia, gastrointestinal tract,heart, kidney, liver, lung, muscle, ovary, pancreas, parathyroid, penis,prostate, salivary glands, skin, spleen, testis, thymus, thyroid, anduterus.

In another embodiment, a vector capable of expressing AFB1-hAR, or afragment or a derivative thereof, may also be administered to a subjectto treat a neoplastic disorder including, but not limited to, thosedescribed above.

In still another embodiment, an agonist which modulates the activity ofAFB1-hAR may also be administered to a subject to treat a neoplasticdisorder including, but not limited to, those described above.

In other embodiments, any of the proteins, antagonists, antibodies,agonists, complementary sequences or vectors of the invention may beadministered in combination with other appropriate therapeutic agents.Selection of the appropriate agents for use in combination therapy maybe made by one of ordinary skill in the art, according to conventionalpharmaceutical principles. The combination of therapeutic agents may actsynergistically to effect the treatment or prevention of the variousdisorders described above. Using this approach, one may be able toachieve therapeutic efficacy with lower dosages of each agent, thusreducing the potential for adverse side effects.

An antagonist of AFB1-hAR may be produced using methods which aregenerally known in the art. In particular, purified AFB1-hAR may be usedto produce antibodies or to screen libraries of pharmaceutical agents toidentify those which specifically bind AFB1-hAR.

Antibodies to AFB1-hAR may be generated using methods that are wellknown in the art. Such antibodies may include, but are not limited to,polyclonal, monoclonal, chimeric, single chain, Fab fragments, andfragments produced by a Fab expression library. Neutralizing antibodies,(i.e., those which inhibit dimer formation) are especially preferred fortherapeutic use.

For the production of antibodies, various hosts including goats,rabbits, rats, mice, humans, and others, may be immunized by injectionwith AFB1-hAR or any fragment or oligopeptide thereof which hasimmunogenic properties. Depending on the host species, various adjuvantsmay be used to increase immunological response. Such adjuvants include,but are not limited to, Freund's, mineral gels such as aluminumhydroxide, and surface active substances such as lysolecithin, pluronicpolyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanin,and dinitrophenol. Among adjuvants used in humans, BCG (bacilliCalmette-Guerin) and Corynebacterium parvum are especially preferable.

It is preferred that the oligopeptides, peptides, or fragments used toinduce antibodies to AFB1-hAR have an amino acid sequence consisting ofat least five amino acids and more preferably at least 10 amino acids.It is also preferable that they are identical to a portion of the aminoacid sequence of the natural protein, and they may contain the entireamino acid sequence of a small, naturally occurring molecule. Shortstretches of AFB1-hAR amino acids may be fused with those of anotherprotein such as keyhole limpet hemocyanin and antibody produced againstthe chimeric molecule.

Monoclonal antibodies to AFB1-hAR may be prepared using any techniquewhich provides for the production of antibody molecules by continuouscell lines in culture. These include, but are not limited to, thehybridoma technique, the human B-cell hybridoma technique, and theEBV-hybridoma technique (Kohler, G. et al. (1975) Nature 256:495-497;Kozbor, D. et al. (1985) J. Immunol. Methods 81:31-42; Cote, R. J. etal. (1983) Proc. Natl. Acad. Sci. 80:2026-2030; Cole, S. P. et al.(1984) Mol. Cell Biol. 62:109-120).

In addition, techniques developed for the production of "chimericantibodies", the splicing of mouse antibody genes to human antibodygenes to obtain a molecule with appropriate antigen specificity andbiological activity can be used (Morrison, S. L. et al. (1984) Proc.Natl. Acad. Sci. 81:6851-6855; Neuberger, M. S. et al. (1984) Nature312:604-608; Takeda, S. et al. (1985) Nature 314:452-454).Alternatively, techniques described for the production of single chainantibodies may be adapted, using methods known in the art, to produceAFB1-hAR-specific single chain antibodies. Antibodies with relatedspecificity, but of distinct idiotypic composition, may be generated bychain shuffling from random combinatorial immunoglobulin libraries(Burton D. R. (1991) Proc. Natl. Acad. Sci. 88:11120-3).

Antibodies may also be produced by inducing in vivo production in thelymphocyte population or by screening immunoglobulin libraries or panelsof highly specific binding reagents as disclosed in the literature(Orlandi, R. et al. (1989) Proc. Natl. Acad. Sci. 86: 3833-3837; Winter,G. et al. (1991) Nature 349:293-299).

Antibody fragments which contain specific binding sites for AFB1-hAR mayalso be generated. For example, such fragments include, but are notlimited to, the F(ab')2 fragments which can be produced by pepsindigestion of the antibody molecule and the Fab fragments which can begenerated by reducing the disulfide bridges of the F(ab')2 fragments.Alternatively, Fab expression libraries may be constructed to allowrapid and easy identification of monoclonal Fab fragments with thedesired specificity (Huse, W. D. et al. (1989) Science 254:1275-1281).

Various immunoassays may be used for screening to identify antibodieshaving the desired specificity. Numerous protocols for competitivebinding or immunoradiometric assays using either polyclonal ormonoclonal antibodies with established specificities are well known inthe art. Such immunoassays typically involve the measurement of complexformation between AFB1-hAR and its specific antibody. A two-site,monoclonal-based immunoassay utilizing monoclonal antibodies reactive totwo non-interfering AFB1-hAR epitopes is preferred, but a competitivebinding assay may also be employed (Maddox, supra).

In another embodiment of the invention, the polynucleotides encodingAFB1-hAR, or any fragment or complement thereof, may be used fortherapeutic purposes. In one aspect, the complement of thepolynucleotide encoding AFB1-hAR may be used in situations in which itwould be desirable to block the transcription of the mRNA. Inparticular, cells may be transformed with sequences complementary topolynucleotides encoding AFB1-hAR Thus, complementary molecules orfragments may be used to modulate AFB1-hAR activity, or to achieveregulation of gene function. Such technology is now well known in theart, and sense or antisense oligonucleotides or larger fragments, can bedesigned from various locations along the coding or control regions ofsequences encoding AFB1-hAR.

Expression vectors derived from retro viruses, adenovirus, herpes orvaccinia viruses, or from various bacterial plasmids may be used fordelivery of nucleotide sequences to the targeted organ, tissue or cellpopulation. Methods which are well known to those skilled in the art canbe used to construct vectors which will express nucleic acid sequencewhich is complementary to the polynucleotides of the gene encodingAFB1-hAR. These techniques are described both in Sambrook et al. (supra)and in Ausubel et al. (supra).

Genes encoding AFB1-hAR can be turned off by transforming a cell ortissue with expression vectors which express high levels of apolynucleotide or fragment thereof which encodes AFB1-hAR. Suchconstructs may be used to introduce untranslatable sense or antisensesequences into a cell. Even in the absence of integration into the DNA,such vectors may continue to transcribe RNA molecules until they aredisabled by endogenous nucleases. Transient expression may last for amonth or more with a non-replicating vector and even longer ifappropriate replication elements are part of the vector system.

As mentioned above, modifications of gene expression can be obtained bydesigning complementary sequences or antisense molecules (DNA, RNA, orPNA) to the control, 5' or regulatory regions of the gene encodingAFB1-hAR (signal sequence, promoters, enhancers, and introns).Oligonucleotides derived from the transcription initiation site, e.g.,between positions -10 and +10 from the start site, are preferred.Similarly, inhibition can be achieved using "triple helix" base-pairingmethodology. Triple helix pairing is useful because it causes inhibitionof the ability of the double helix to open sufficiently for the bindingof polymerases, transcription factors, or regulatory molecules. Recenttherapeutic advances using triplex DNA have been described in theliterature (Gee, J. E. et al. (1994) In: Huber, B. E. and B. I. Carr,Molecular and Immunologic Approaches, Futura Publishing Co., Mt. Kisco,N.Y.). The complementary sequence or antisense molecule may also bedesigned to block translation of mRNA by preventing the transcript frombinding to ribosomes.

Ribozymes, enzymatic RNA molecules, may also be used to catalyze thespecific cleavage of RNA. The mechanism of ribozyme action involvessequence-specific hybridization of the ribozyme molecule tocomplementary target RNA, followed by endonucleolytic cleavage. Exampleswhich may be used include engineered hammerhead motif ribozyme moleculesthat can specifically and efficiently catalyze endonucleolytic cleavageof sequences encoding AFB1-hAR.

Specific ribozyme cleavage sites within any potential RNA target areinitially identified by scanning the target molecule for ribozymecleavage sites which include the following sequences: GUA, GUU, and GUC.Once identified, short RNA sequences of between 15 and 20ribonucleotides corresponding to the region of the target genecontaining the cleavage site may be evaluated for secondary structuralfeatures which may render the oligonucleotide inoperable. Thesuitability of candidate targets may also be evaluated by testingaccessibility to hybridization with complementary oligonucleotides usingribonuclease protection assays.

Complementary ribonucleic acid molecules and ribozymes of the inventionmay be prepared by any method known in the art for the synthesis ofnucleic acid molecules. These include techniques for chemicallysynthesizing oligonucleotides such as solid phase phosphoramiditechemical synthesis. Alternatively, RNA molecules may be generated by invitro and in vivo transcription of DNA sequences encoding AFB1-hAR. SuchDNA sequences may be incorporated into a wide variety of vectors withsuitable RNA polymerase promoters such-as T7 or SP6. Alternatively,these cDNA constructs that synthesize complementary RNA constitutivelyor inducibly can be introduced into cell lines, cells, or tissues.

RNA molecules may be modified to increase intracellular stability andhalf-life. Possible modifications include, but are not limited to, theaddition of flanking sequences at the 5' and/or 3' ends of the moleculeor the use of phosphorothioate or 2' O-methyl rather thanphosphodiesterase linkages within the backbone of the molecule. Thisconcept is inherent in the production of PNAs and can be extended in allof these molecules by the inclusion of nontraditional bases such asinosine, queosine, and wybutosine, as well as acetyl-, methyl-, thio-,and similarly modified forms of adenine, cytidine, guanine, thymine, anduridine which are not as easily recognized by endogenous endonucleases.

Many methods for introducing vectors into cells or tissues are availableand equally suitable for use in vivo, in vitro and ex vivo. For ex vivotherapy, vectors may be introduced into stem cells taken from thepatient and clonally propagated for autologous transplant back into thatsame patient. Delivery by transfection, by liposome injections orpolycationic amino polymers (Goldman, C. K. et al. (1997) NatureBiotechnology 15:462-66; incorporated herein by reference) may beachieved using methods which are well known in the art.

Any of the therapeutic methods described above may be applied to anysubject in need of such therapy, including, for example, mammals such asdogs, cats, cows, horses, rabbits, monkeys, and most preferably, humans.

An additional embodiment of the invention relates to the administrationof a pharmaceutical composition, in conjunction with a pharmaceuticallyacceptable carrier, for any of the therapeutic effects discussed above.Such pharmaceutical compositions may consist of AFB1-hAR, antibodies toAFB1-hAR, mimetics, agonists, antagonists, or inhibitors of AFB1-hAR.The compositions may be administered alone or in combination with atleast one other agent, such as stabilizing compound, which may beadministered in any sterile, biocompatible pharmaceutical carrier,including, but not limited to, saline, buffered saline, dextrose, andwater. The compositions may be administered to a patient alone, or incombination with other agents, drugs or hormones.

The pharmaceutical compositions utilized in this invention may beadministered by any number of routes including, but not limited to,oral, intravenous, intramuscular, intra-arterial, intramedullary,intrathecal, intraventricular, transdermal, subcutaneous,intraperitoneal, intranasal, enteral, topical, sublingual, or rectalmeans.

In addition to the active ingredients, these pharmaceutical compositionsmay contain suitable pharmaceutically-acceptable carriers comprisingexcipients and auxiliaries which facilitate processing of the activecompounds into preparations which can be used pharmaceutically. Furtherdetails on techniques for formulation and administration may be to foundin the latest edition of Remington's Pharmaceutical Sciences (MaackPublishing Co., Easton, Pa.).

Pharmaceutical compositions for oral administration can be formulatedusing pharmaceutically acceptable carriers well known in the art indosages suitable for oral administration. Such carriers enable thepharmaceutical compositions to be formulated as tablets, pills, dragees,capsules, liquids, gels, syrups, slurries, suspensions, and the like,for ingestion by the patient.

Pharmaceutical preparations for oral use can be obtained throughcombination of active compounds with solid excipient, optionallygrinding a resulting mixture, and processing the mixture of granules,after adding suitable auxiliaries, if desired, to obtain tablets ordragee cores. Suitable excipients are carbohydrate or protein fillers,such as sugars, including lactose, sucrose, mannitol, or sorbitol;starch from corn, wheat, rice, potato, or other plants; cellulose, suchas methyl cellulose, hydroxypropylmethyl-cellulose, or sodiumcarboxymethylcellulose; gums including arabic and tragacanth; andproteins such as gelatin and collagen. If desired, disintegrating orsolubilizing agents may be added, such as the cross-linked polyvinylpyrrolidone, agar, alginic acid, or a salt thereof, such as sodiumalginate.

Dragee cores may be used in conjunction with suitable coatings, such asconcentrated sugar solutions, which may also contain gum arabic, talc,polyvinylpyrrolidone, carbopol gel, polyethylene glycol, and/or titaniumdioxide, lacquer solutions, and suitable organic solvents or solventmixtures. Dyestuffs or pigments may be added to the tablets or drageecoatings for product identification or to characterize the quantity ofactive compound, i.e., dosage.

Pharmaceutical preparations which can be used orally include push-fitcapsules made of gelatin, as well as soft, sealed capsules made ofgelatin and a coating, such as glycerol or sorbitol. Push-fit capsulescan contain active ingredients mixed with a filler or binders, such aslactose or starches, lubricants, such as talc or magnesium stearate,and, optionally, stabilizers. In soft capsules, the active compounds maybe dissolved or suspended in suitable liquids, such as fatty oils,liquid, or liquid polyethylene glycol with or without stabilizers.

Pharmaceutical formulations suitable for parenteral administration maybe formulated in aqueous solutions, preferably in physiologicallycompatible buffers such as Hanks' solution, Ringer's solution, orphysiologically buffered saline. Aqueous injection suspensions maycontain substances which increase the viscosity of the suspension, suchas sodium carboxymethyl cellulose, sorbitol, or dextran. Additionally,suspensions of the active compounds may be prepared as appropriate oilyinjection suspensions. Suitable lipophilic solvents or vehicles includefatty oils such as sesame oil, or synthetic fatty acid esters, such asethyl oleate or triglycerides, or liposomes. Non-lipid polycationicamino polymers may also be used for delivery. Optionally, the suspensionmay also contain suitable stabilizers or agents which increase thesolubility of the compounds to allow for the preparation of highlyconcentrated solutions.

For topical or nasal administration, penetrants appropriate to theparticular barrier to be permeated are used in the formulation. Suchpenetrants are generally known in the art.

The pharmaceutical compositions of the present invention may bemanufactured in a manner that is known in the art, e.g., by means ofconventional mixing, dissolving, granulating, dragee-making, levigating,emulsifying, encapsulating, entrapping, or lyophilizing processes.

The pharmaceutical composition may be provided as a salt and can beformed with many acids, including but not limited to, hydrochloric,sulfuric, acetic, lactic, tartaric, malic, succinic, etc. Salts tend tobe more soluble in aqueous or other protonic solvents than are thecorresponding free base forms. In other cases, the preferred preparationmay be a lyophilized powder which may contain any or all of thefollowing: 1-50 mM histidine, 0.1%-2% sucrose, and 2-7% mannitol, at apH range of 4.5 to 5.5, that is combined with buffer prior to use.

After pharmaceutical compositions have been prepared, they can be placedin an appropriate container and labeled for treatment of an indicatedcondition. For administration of AFB1-hAR, such labeling would includeamount, frequency, and method of administration.

Pharmaceutical compositions suitable for use in the invention includecompositions wherein the active ingredients are contained in aneffective amount to achieve the intended purpose. The determination ofan effective dose is well within the capability of those skilled in theart.

For any compound, the therapeutically effective dose can be estimatedinitially either in cell culture assays, e.g., of neoplastic cells, orin animal models, usually mice, rabbits, dogs, or pigs. The animal modelmay also be used to determine the appropriate concentration range androute of administration. Such information can then be used to determineuseful doses and routes for administration in humans.

A therapeutically effective dose refers to that amount of activeingredient, for example AFB1-hAR or fragments thereof, antibodies ofAFB1-hAR, agonists, antagonists or inhibitors of AFB1-hAR, whichameliorates the symptoms or condition. Therapeutic efficacy and toxicitymay be determined by standard pharmaceutical procedures in cell culturesor experimental animals, e.g., ED50 (the dose therapeutically effectivein 50% of the population) and LD50 (the dose lethal to 50% of thepopulation). The dose ratio between therapeutic and toxic effects is thetherapeutic index, and it can be expressed as the ratio, LD50/ED50.Pharmaceutical compositions which exhibit large therapeutic indices arepreferred. The data obtained from cell culture assays and animal studiesis used in formulating a range of dosage for human use. The dosagecontained in such compositions is preferably within a range ofcirculating concentrations that include the ED50 with little or notoxicity. The dosage varies within this range depending upon the dosageform employed, sensitivity of the patient, and the route ofadministration.

The exact dosage will be determined by the practitioner, in light offactors related to the subject that requires treatment. Dosage andadministration are adjusted to provide sufficient levels of the activemoiety or to maintain the desired effect. Factors which may be takeninto account include the severity of the disease state, general healthof the subject, age, weight, and gender of the subject, diet, time andfrequency of administration, drug combination(s), reactionsensitivities, and tolerance/response to therapy. Long-actingpharmaceutical compositions may be administered every 3 to 4 days, everyweek, or once every two weeks depending on half-life and clearance rateof the particular formulation.

Normal dosage amounts may vary from 0.1 to 100,000 micrograms, up to atotal dose of about 1 g, depending upon the route of administration.Guidance as to particular dosages and methods of delivery is provided inthe literature and generally available to practitioners in the art.Those skilled in the art will employ different formulations fornucleotides than for proteins or their inhibitors. Similarly, deliveryof polynucleotides or polypeptides will be specific to particular cells,conditions, locations, etc.

Diagnostics

In another embodiment, antibodies which specifically bind AFB1-hAR maybe used for the diagnosis of conditions or diseases characterized byexpression of AFB1-hAR, or in assays to monitor patients being treatedwith AFB1-hAR, agonists, antagonists or inhibitors. The antibodiesuseful for diagnostic purposes may be prepared in the same manner asthose described above for therapeutics. Diagnostic assays for AFB1-hARinclude methods which utilize the antibody and a label to detectAFB1-hAR in human body fluids or extracts of cells or tissues. Theantibodies may be used with or without modification, and may be labeledby joining them, either covalently or non-covalently, with a reportermolecule. A wide variety of reporter molecules which are known in theart may be used, several of which are described above.

A variety of protocols including ELISA, RIA, and FACS for measuringAFB1-hAR are known in the art and provide a basis for diagnosing alteredor abnormal levels of AFB1-hAR expression. Normal or standard values forAFB1-hAR expression are established by combining body fluids or cellextracts taken from normal mammalian subjects, preferably human, withantibody to AFB1-hAR under conditions suitable for complex formation.The amount of standard complex formation may be quantified by variousmethods, but preferably by photometric, means. Quantities of AFB1-hARexpressed in control and disease samples from biopsied tissues arecompared with the standard values. Deviation between standard andsubject values establishes the parameters for diagnosing disease.

In another embodiment of the invention, the polynucleotides encodingAFB1-hAR may be used for diagnostic purposes. The polynucleotides whichmay be used include oligonucleotide sequences, complementary RNA and DNAmolecules, and PNAs. The polynucleotides may be used to detect andquantitate gene expression in biopsied tissues in which expression ofAFB1-hAR may be correlated with disease. The diagnostic assay may beused to distinguish between absence, presence, and excess expression ofAFB1-hAR, and to monitor regulation of AFB1-hAR levels duringtherapeutic intervention.

In one aspect, hybridization with PCR probes which are capable ofdetecting polynucleotide sequences, including genomic sequences,encoding AFB1-hAR or closely related molecules, may be used to identifynucleic acid sequences which encode AFB1-hAR. The specificity of theprobe, whether it is made from a highly specific region, e.g., 10 uniquenucleotides in the 5' regulatory region, or a less specific region,e.g., especially in the 3' coding region, and the stringency of thehybridization or amplification (maximal, high, intermediate, or low)will determine whether the probe identifies only naturally occurringsequences encoding AFB1-hAR, alleles, or related sequences.

Probes may also be used for the detection of related sequences, andshould preferably contain at least 50% of the nucleotides from any ofthe AFB1-hAR encoding sequences. The hybridization probes of the subjectinvention may be DNA or RNA and derived from the nucleotide sequence ofSEQ ID NO:2 or from genomic sequence including promoter, enhancerelements, and introns of the naturally occurring AFB1-hAR.

Means for producing specific hybridization probes for DNAs encodingAFB1-hAR include the cloning of nucleic acid sequences encoding AFB1-hARor AFB1-hAR derivatives into vectors for the production of mRNA probes.Such vectors are known in the art, commercially available, and may beused to synthesize RNA probes in vitro by means of the addition of theappropriate RNA polymerases and the appropriate labeled nucleotides.Hybridization probes may be labeled by a variety of reporter groups, forexample, radionuclides such as 32P or 35S, or enzymatic labels, such asalkaline phosphatase coupled to the probe via avidin/biotin couplingsystems, and the like.

Polynucleotide sequences encoding AFB1-hAR may be used for the diagnosisof conditions or disorders which are associated with expression ofAFB1-hAR. Examples of such conditions or disorders includegastrointestinal disorders such as ascites, cholelithiasis,cholecystitis, cirrhosis, Crohn's disease, diverticulitis, fulminanthepatitis, gastritis, gastric and duodenal ulcers, hepatorenal syndrome,irritable bowel syndrome, jaundice, pancreatitis, and ulcerativecolitis, and neoplastic disorders such as adenocarcinoma, leukemia,lymphoma, melanoma, myeloma, sarcoma, and teratocarcinoma, andparticularly cancers of the adrenal gland, bladder, bone, bone marrow,brain, breast, cervix, gall bladder, ganglia, gastrointestinal tract,heart, kidney, liver, lung, muscle, ovary, pancreas, parathyroid, penis,prostate, salivary glands, skin, spleen, testis, thymus, thyroid, anduterus. The polynucleotide sequences encoding AFB1-hAR may be used inSouthern or northern analysis, dot blot, or other membrane-basedtechnologies; in PCR technologies; or in dipstick, pin, ELISA assays ormicroarrays utilizing fluids or tissues from patient biopsies to detectaltered AFB1-hAR expression. Such qualitative or quantitative methodsare well known in the art.

In a particular aspect, the nucleotide sequences encoding AFB1-hAR maybe useful in assays that detect activation or induction of variouscancers, particularly those mentioned above. The nucleotide sequencesencoding AFB1-hAR may be labeled by standard methods, and added to afluid or tissue sample from a patient under conditions suitable for theformation of hybridization complexes. After a suitable incubationperiod, the sample is washed and the signal is quantitated and comparedwith a standard value. If the amount of signal in the biopsied orextracted sample is significantly altered from that of a comparablecontrol sample, the nucleotide sequences have hybridized with nucleotidesequences in the sample, and the presence of altered levels ofnucleotide sequences encoding AFB1-hAR in the sample indicates thepresence of the associated disease. Such assays may also be used toevaluate the efficacy of a particular therapeutic treatment regimen inanimal studies, in clinical trials, or in monitoring the treatment of anindividual patient.

In order to provide a basis for the diagnosis of disease associated withexpression of AFB1-hAR, a normal or standard profile for expression isestablished. This may be accomplished by combining body fluids or cellextracts taken from normal subjects, either animal or human, with asequence, or a fragment thereof, which encodes AFB1 -hAR, underconditions suitable for hybridization or amplification. Standardhybridization may be quantified by comparing the values obtained fromnormal subjects with those from an experiment where a known amount of asubstantially purified polynucleotide is used. Standard values-obtainedfrom normal samples may be compared with values obtained from samplesfrom patients who are symptomatic for disease. Deviation betweenstandard and subject values is used to establish the presence ofdisease.

Once disease is established and a treatment protocol is initiated,hybridization assays may be repeated on a regular basis to evaluatewhether the level of expression in the patient begins to approximatethat which is observed in the normal patient. The results obtained fromsuccessive assays may be used to show the efficacy of treatment over aperiod ranging from several days to months.

With respect to cancer, the presence of a relatively high amount oftranscript in biopsied tissue from an individual may indicate apredisposition for the development of the disease, or may provide ameans for detecting the disease prior to the appearance of actualclinical symptoms. A more definitive diagnosis of this type may allowhealth professionals to employ preventative measures or aggressivetreatment earlier thereby preventing the development or furtherprogression of the cancer.

Additional diagnostic uses for oligonucleotides designed from thesequences encoding AFB1-hAR may involve the use of PCR. Such oligomersmay be chemically synthesized, generated enzymatically, or produced invitro. Oligomers will preferably consist of two nucleotide sequences,one with sense orientation (5'->3') and another with antisense (3'<-5'),employed under optimized conditions for identification of a specificgene or condition. The same two oligomers, nested sets of oligomers, oreven a degenerate pool of oligomers may be employed under less stringentconditions for detection and/or quantitation of closely related DNA orRNA sequences.

Methods which may also be used to quantitate the expression of AFB1-hARinclude radiolabeling or biotinylating nucleotides, coamplification of acontrol nucleic acid, and standard curves onto which the experimentalresults are interpolated (Melby, P. C. et al. (1993) J. Immunol.Methods, 159:235-244; Duplaa, C. et al. (1993) Anal. Biochem.212:229-236). The speed of quantitation of multiple samples may beaccelerated by running the assay in an ELISA format where the oligomerof interest is presented in various dilutions and a spectrophotometricor colorimetric response gives rapid quantitation.

In further embodiments, an oligonucleotide derived from any of thepolynucleotide sequences described herein may be used as a target in amicroarray. The microarray can be used to monitor the expression levelof large numbers of genes simultaneously (to produce a transcriptimage), and to identify genetic variants, mutations and polymorphisms.This information will be useful in determining gene function,understanding the genetic basis of disease, diagnosing disease, and indeveloping and monitoring the activity of therapeutic agents (Heller, R.et al. (1997) Proc. Natl. Acad. Sci. 94:2150-55).

In one embodiment, the microarray is prepared and used according to themethods described in PCT application WO95/11995 (Chee et al.), Lockhart,D. J. et al. (1996; Nat. Biotech. 14: 1675-1680) and Schena, M. et al.(1996; Proc. Natl. Acad. Sci. 93: 10614-10619), all of which areincorporated herein in their entirety by reference.

The microarray is preferably composed of a large number of unique,single-stranded nucleic acid sequences, usually either syntheticantisense oligonucleotides or fragments of cDNAs, fixed to a solidsupport. The oligonucleotides are preferably about 6-60 nucleotides inlength, more preferably 15-30 nucleotides in length, and most preferablyabout 20-25 nucleotides in length. For a certain type of microarray, itmay be preferable to use oligonucleotides which are only 7-10nucleotides in length. The microarray may contain oligonucleotides whichcover the known 5', or 3', sequence, sequential oligonucleotides whichcover the full length sequence; or unique oligonucleotides selected fromparticular areas along the length of the sequence. Polynucleotides usedin the microarray may be oligonucleotides that are specific to a gene orgenes of interest in which at least a fragment of the sequence is knownor that are specific to one or more unidentified cDNAs which are commonto a particular cell type, developmental or disease state.

In order to produce oligonucleotides to a known sequence for amicroarray, the gene of interest is examined using a computer algorithmwhich starts at the 5' or more preferably at the 3' end of thenucleotide sequence. The algorithm identifies oligomers of definedlength that are unique to the gene, have a GC content within a rangesuitable for hybridization, and lack predicted secondary structure thatmay interfere with hybridization. In certain situations it may beappropriate to use pairs of oligonucleotides on a microarray. The"pairs" will be identical, except for one nucleotide which preferably islocated in the center of the sequence. The second oligonucleotide in thepair (mismatched by one) serves as a control. The number ofoligonucleotide pairs may range from two to one million. The oligomersare synthesized at designated areas on a substrate using alight-directed chemical process. The substrate may be paper, nylon orother type of membrane, filter, chip, glass slide or any other suitablesolid support.

In another aspect, an oligonucleotide may be synthesized on the surfaceof the substrate by using a chemical coupling procedure and an ink jetapplication apparatus, as described in PCT application WO95/251116(Baldeschweiler et al.) which is incorporated herein in its entirety byreference. In another aspect, a "gridded" array analogous to a dot (orslot) blot may be used to arrange and link cDNA fragments oroligonucleotides to the surface of a substrate using a vacuum system,thermal, UV, mechanical or chemical bonding procedures. An array, suchas those described above, may be produced by hand or by using availabledevices (slot blot or dot blot apparatus), materials (any suitable solidsupport), and machines (including robotic instruments), and may contain8, 24, 96, 384, 1536 or 6144 oligonucleotides, or any other numberbetween two and one million which lends itself to the efficient use ofcommercially available instrumentation.

In order to conduct sample analysis using a microarray, the RNA or DNAfrom a biological sample is made into hybridization probes. The mRNA isisolated, and cDNA is produced and used as a template to make antisenseRNA (aRNA). The aRNA is amplified in the presence of fluorescentnucleotides, and labeled probes are incubated with the microarray sothat the probe sequences hybridize to complementary oligonucleotides ofthe microarray. Incubation conditions are adjusted so that hybridizationoccurs with precise complementary matches or with various degrees ofless complementarity. After removal of nonhybridized probes, a scanneris used to determine the levels and patterns of fluorescence. Thescanned images are examined to determine degree of complementarity andthe relative abundance of each oligonucleotide sequence on themicroarray. The biological samples may be obtained from any bodilyfluids (such as blood, urine, saliva, phlegm, gastric juices, etc.),cultured cells, biopsies, or other tissue preparations. A detectionsystem may be used to measure the absence, presence, and amount ofhybridization for all of the distinct sequences simultaneously. Thisdata may be used for large scale correlation studies on the sequences,mutations, variants, or polymorphisms among samples.

In another embodiment of the invention, the nucleic acid sequences whichencode AFB1-hAR may also be used to generate hybridization probes whichare useful for mapping the naturally occurring genomic sequence. Thesequences may be mapped to a particular chromosome, to a specific regionof a chromosome or to artificial chromosome constructions, such as humanartificial chromosomes (HACs), yeast artificial chromosomes (YACs),bacterial artificial chromosomes (BACs), bacterial PI constructions orsingle chromosome cDNA libraries as reviewed in Price, C. M. (1993)Blood Rev. 7:127-134, and Trask, B. J. (1991) Trends Genet. 7:149-154.

Fluorescent in situ hybridization (FISH as described in Verma et al.(1988) Human Chromosomes: A Manual of Basic Techniques, Pergamon Press,New York, N.Y.) may be correlated with other physical chromosome mappingtechniques and genetic map data. Examples of genetic map data can befound in various scientific journals or at Online Mendelian Inheritancein Man (OMIM). Correlation between the location of the gene encodingAFB1-hAR on a physical chromosomal map and a specific disease, orpredisposition to a specific disease, may help delimit the region of DNAassociated with that genetic disease. The nucleotide sequences of thesubject invention may be used to detect differences in gene sequencesbetween normal, carrier, or affected individuals.

In situ hybridization of chromosomal preparations and physical mappingtechniques such as linkage analysis using established chromosomalmarkers may be used for extending genetic maps. Often the placement of agene on the chromosome of another mammalian species, such as mouse, mayreveal associated markers even if the number or arm of a particularhuman chromosome is not known. New sequences can be assigned tochromosomal arms, or parts thereof, by physical mapping. This providesvaluable information to investigators searching for disease genes usingpositional cloning or other gene discovery techniques. Once the diseaseor syndrome has been crudely localized by genetic linkage to aparticular genomic region, for example, AT to 11q22-23 (Gatti, R. A. etal. (1988) Nature 336:577-580), any sequences mapping to that area mayrepresent associated or regulatory genes for further investigation. Thenucleotide sequence of the subject invention may also be used to detectdifferences in the chromosomal location due to translocation, inversion,etc. among normal, carrier, or affected individuals.

In another embodiment of the invention, AFB1-hAR, its catalytic orimmunogenic fragments or oligopeptides thereof, can be used forscreening libraries of compounds in any of a variety of drug screeningtechniques. The fragment employed in such screening may be free insolution, affixed to a solid support, borne on a cell surface, orlocated intracellularly. The formation of binding complexes, betweenAFB1-hAR and the agent being tested, may be measured.

Another technique for drug screening which may be used provides for highthroughput screening of compounds having suitable binding affinity tothe protein of interest as described in published PCT applicationWO84/03564. In this method, as applied to AFB1-hAR large numbers ofdifferent small test compounds are synthesized on a solid substrate,such as plastic pins or some other surface. The test compounds arereacted with AFB1-hAR, or fragments thereof, and washed. Bound AFB1-hARis then detected by methods well known in the art. Purified AFB1-hAR canalso be coated directly onto plates for use in the aforementioned drugscreening techniques. Alternatively, non-neutralizing antibodies can beused to capture the peptide and immobilize it on a solid support.

In another embodiment, one may use competitive drug screening assays inwhich neutralizing antibodies capable of binding AFB1-hAR specificallycompete with a test compound for binding AFB1-hAR. In this manner, theantibodies can be used to detect the presence of any peptide whichshares one or more antigenic determinants with AFB1-hAR.

In additional embodiments, the nucleotide sequences which encodeAFB1-hAR may be used in any molecular biology techniques that have yetto be developed, provided the new techniques rely on properties ofnucleotide sequences that are currently known, including, but notlimited to, such properties as the triplet genetic code and specificbase pair interactions.

The examples below are provided to illustrate the subject invention andare not included for the purpose of limiting the invention.

EXAMPLES

I BRAINOT14 cDNA Library Construction

The BRAINOT14 cDNA library was prepared from nontumorous brain tissueremoved from the left frontal lobe of a 40-year-old Caucasian femaleduring excision of a cerebral meningeal lesion. Pathology for theassociated tumor tissue indicated grade 4 gemistocytic astrocytoma. Thepatient presented with coma, epilepsy, incontinence of urine and stool,Type II diabetes, and paralysis. Patient history included chronicnephritis. Patient medications included Decadron (dexamethasone) andphenytoin sodium.

The frozen tissue was homogenized and lysed using a Brinkmann POLYTRONhomogenizer PT-3000 (Brinkmann Instruments, Westbury, N.J.) inguanidinium isothiocyanate solution. The lysate was centrifuged over a5.7M CsCl cushion using an Beckman SW28 rotor in a Beckman L8-70Multracentrifuge (Beckman Instruments) for 18 hours at 25,000 rpm atambient temperature. The RNA was extracted with acid phenol pH 4.7,precipitated using 0.3M sodium acetate and 2.5 volumes of ethanol,resuspended in RNAse-free water, and treated with DNase at 37° C. TheRNA extraction and precipitation were repeated as before.

The mRNA was isolated with the OLIGOTEX kit (QIAGEN, Inc.; Chatsworth,Calif.) and used to construct the cDNA library. The mRNA was handledaccording to the recommended protocols in the SUPERSCRIPT plasmid system(Cat. #18248-013; Gibco/BRL). BRAINOT14 cDNAs were fractionated on aSEPHAROSE CL4B column (Cat. #275105-01; Pharmacia), and those cDNAsexceeding 400 bp were ligated into pINCY 1. The plasmid pINCY 1 wassubsequently transformed into DH50C" competent cells (Cat. #18258-012;Gibco/BRL).

II Isolation and Sequencing of cDNA Clones

Plasmid DNA was purified using the MINIPREP Kit (Catalogue #77468,Advanced Genetic Technologies Corporation, Gaithersburg MD.), a 96-wellblock kit with reagents for 960 purifications. The recommended protocolincluded with the kit was employed except for the following changes.Each of the 96 wells was filled with only 1 ml of sterile Terrific Broth(Catalog # 22711, GIBCO/BRL) with carbenicillin at 25 mg/L and glycerolat 0.4%. After the wells were inoculated, the bacteria were cultured for24 hours and lysed with 60 μl of lysis buffer. A centrifugation step(Beckman GS-6R @2900 rpm for 5 min; Beckman Instruments) was performedbefore the contents of the block were added to the primary filter plate.The optional step of adding isopropanol to TRIS buffer was not routinelyperformed. After the last step in the protocol, samples were transferredto a Beckman 96-well block for storage.

The cDNAs were sequenced by the method of Sanger F. and A. R. Coulson(1975; J Mol Biol 94:441f), using a Hamilton MICROBLAB 2200 (Hamilton,Reno Nev.) in combination with four Peltier thermal cyclers (PTC200 fromM J Research, Watertown Mass.) and Applied Biosystems 377 or 373 DNAsequencing systems (Perkin Elmer), and the reading frame was determined.

III Homology Searching of cDNA Clones and Their Deduced Proteins

The nucleotide sequences of the Sequence Listing or amino acid sequencesdeduced from them were used as query sequences against databases such asGenBank, SwissProt, BLOCKS, and Pima II. These databases which containpreviously identified and annotated sequences were searched for regionsof homology (similarity) using BLAST, which stands for Basic LocalAlignment Search Tool (Altschul, S. F. (1993) J.. Mol. Evol. 36:290-300;Altschul et al. (1990) J. Mol. Biol. 215:403-410).

BLAST produces alignments of both nucleotide and amino acid sequences todetermine sequence similarity. Because of the local nature of thealignments, BLAST is especially useful in determining exact matches orin identifying homologs which may be of prokaryotic (bacterial) oreukaryotic (animal, fungal or plant) origin. Other algorithms such asthe one described in Smith R. F. and T. F. Smith (1992; ProteinEngineering 5:35-51), incorporated herein by reference, can be used whendealing with primary sequence patterns and secondary structure gappenalties. As disclosed in this application, the sequences have lengthsof at least 49 nucleotides, and no more than 12% uncalled bases (where Nis recorded rather than A, C, G, or T).

The BLAST approach, as detailed in Karlin, S. and S. F. Altschul (1993;Proc. Nat. Acad. Sci. 90:5873-7) and incorporated herein by reference,searches for matches between a query sequence and a database sequence,to evaluate the statistical significance of any matches found, and toreport only those matches which satisfy the user-selected threshold ofsignificance. In this application, threshold was set at 10⁻²⁵ fornucleotides and 10⁻¹⁴ for peptides.

Incyte nucleotide sequences were searched against the GenBank databasesfor primate (pri), rodent (rod), and mammalian sequences (mam), anddeduced amino acid sequences from the same clones are searched againstGenBank functional protein databases, mammalian (mamp), vertebrate(vrtp) and eukaryote (eukp), for homology.

IV Northern Analysis

Northern analysis is a laboratory technique used to detect the presenceof a transcript of a gene and involves the hybridization of a labelednucleotide sequence to a membrane on which RNAs from a particular celltype or tissue have been bound (Sambrook et al., supra).

Analogous computer techniques using BLAST (Altschul, S. F. (1993) J.Mol. Evol. 36:290-300; Altschul, S. F. et al. (1990) J. Mol. Evol.215:403-410) are used to search for identical or related molecules innucleotide databases such as GenBank or the LIFESEQ™ database (IncytePharmaceuticals). This analysis is much faster than multiple,membrane-based hybridizations. In addition, the sensitivity of thecomputer search can be modified to determine whether any particularmatch is categorized as exact or homologous.

The basis of the search is the product score which is defined as:##EQU1## The product score takes into account both the degree ofsimilarity between two sequences and the length of the sequence match.For example, with a product score of 40, the match will be exact withina 1-2% error; and at 70, the match will be exact. Homologous moleculesare usually identified by selecting those which show product scoresbetween 15 and 40, although lower scores may identify related molecules.

The results of northern analysis are reported as a list of libraries inwhich the transcript encoding AFB1-hAR occurs. Abundance and percentabundance are also reported. Abundance directly reflects the number oftimes a particular transcript is represented in a cDNA library, andpercent abundance is abundance divided by the total number of sequencesexamined in the cDNA library.

V Extension of AFB1-hAR Encoding Polynucleotides

The nucleic acid sequence of the Incyte Clone 1596452 was used to designoligonucleotide primers for extending a partial nucleotide sequence tofull length. One primer was synthesized to initiate extension in theantisense direction, and the other was synthesized to extend sequence inthe sense direction. Primers were used to facilitate the extension ofthe known sequence "outward" generating amplicons containing new,unknown nucleotide sequence for the region of interest. The initialprimers were designed from the cDNA using OLIGO 4.06 software (NationalBiosciences), or another appropriate program, to be about 22 to about 30nucleotides in length, to have a GC content of 50% or more, and toanneal to the target sequence at temperatures of about 68° to about 72°C. Any stretch of nucleotides which would result in hairpin structuresand primer--primer dimerizations was avoided.

Selected human cDNA libraries (Gibco/BRL) were used to extend thesequence. If more than one extension is necessary or desired, additionalsets of primers are designed to further extend the known region.

High fidelity amplification was obtained by following the instructionsfor the XL-PCR kit (Perkin Elmer) and thoroughly mixing the enzyme andreaction mix. Beginning with 40 pmol of each primer and the recommendedconcentrations of all other components of the kit, PCR was performedusing the Peltier thermal cycler (PTC200; M. J. Research, Watertown,Mass.) and the following parameters:

    ______________________________________                                        Step 1       94° C. for 1 min (initial denaturation)                                 Step 2  65° C. for 1 min                                   Step 3  68° C. for 6 min                                               Step 4  94° C. for 15 sec                                              Step 5  65° C. for 1 min                                               Step 6  68° C. for 7 min                                               Step 7  Repeat step 4-6 for 15 additional cycles                              Step 8  94° C. for 15 sec                                              Step 9  65° C. for 1 min                                               Step 10 68° C. for 7:15 min                                            Step 11 Repeat step 8-10 for 12 cycles                                        Step 12 72° C. for 8 min                                               Step 13 4° C. (and holding)                                          ______________________________________                                    

A 5-10 μl aliquot of the reaction mixture was analyzed byelectrophoresis on a low concentration (about 0.6-0.8%) agarose mini-gelto determine which reactions were successful in extending the sequence.Bands thought to contain the largest products were excised from the gel,purified using QIAQUICK DNA gel purification kit (QIAGEN Inc.,Chatsworth, Calif.), and trimmed of overhangs using Klenow enzyme tofacilitate religation and cloning.

After ethanol precipitation, the products were redissolved in 13 μl ofligation buffer, 1 μl T4-DNA ligase (15 units) and 1 μl T4polynucleotide kinase were added, and the mixture was incubated at roomtemperature for 2-3 hours or overnight at 160 C. Competent E. coli cells(in 40 μl of appropriate media) were transformed with 3 μl of ligationmixture and cultured in 80 μl of SOC medium (Sambrook et al., supra).After incubation for one hour at 37° C., the E. coli mixture was platedon Luria Bertani (LB)-agar (Sambrook et al., supra) containing 2× Carb.The following day, several colonies were randomly picked from each plateand cultured in 150 μl of liquid LB/2× Carb medium placed in anindividual well of an appropriate, commercially-available, sterile96-well microtiter plate. The following day, 5 μl of each overnightculture was transferred into a non-sterile 96-well plate and afterdilution 1:10 with water, 5 μl of each sample was transferred into a PCRarray.

For PCR amplification, 18 μl of concentrated PCR reaction mix (3.3×)containing 4 units of rTth DNA polymerase, a vector primer, and one orboth of the gene specific primers used for the extension reaction wereadded to each well. Amplification was performed using the followingconditions:

    ______________________________________                                        Step 1      94° C. for 60 sec                                            Step 2 94° C. for 20 sec                                               Step 3 55° C. for 30 sec                                               Step 4 72° C. for 90 sec                                               Step 5 Repeat steps 2-4 for an additional 29 cycles                           Step 6 72° C. for 180 sec                                              Step 7  4° C. (and holding)                                          ______________________________________                                    

Aliquots of the PCR reactions were run on agarose gels together withmolecular weight markers. The sizes of the PCR products were compared tothe original partial cDNAs, and appropriate clones were selected,ligated into plasmid, and sequenced.

In like manner, the nucleotide sequence of SEQ ID NO:2 is used to obtain5' regulatory sequences using the procedure above, oligonucleotidesdesigned for 5' extension, and an appropriate genomic library.

VI Labeling and Use of Individual Hybridization Probes

Hybridization probes derived from SEQ ID NO:2 are employed to screencDNAs, genomic DNAs, or mRNAs. Although the labeling ofoligonucleotides, consisting of about 20 base-pairs, is specificallydescribed, essentially the same procedure is used with larger nucleotidefragments. Oligonucleotides are designed using state-of-the-art softwaresuch as OLIGO 4.06 software (National Biosciences), labeled by combining50 pmol of each oligomer and 250 μCi of [γ-³² P] adenosine triphosphate(Amersham) and T4 polynucleotide kinase (DuPont NEN®, Boston, Mass.).The labeled oligonucleotides are substantially purified with SEPHADEXG-25 superfine resin column (Pharmacia & Upjohn). A aliquot containing10⁷ counts per minute of the labeled probe is used in a typicalmembrane-based hybridization analysis of human genomic DNA digested withone of the following endonucleases (Ase I, Bgl II, Eco RI, Pst I, Xba 1,or Pvu II; DuPont NEN®).

The DNA from each digest is fractionated on a 0.7 percent agarose geland transferred to nylon membranes NYTRAN PLUS membrane, Schleicher &Schuell, Durham, N.H.). Hybridization is carried out for 16 hours at 40°C. To remove nonspecific signals, blots are sequentially washed at roomtemperature under increasingly stringent conditions up to 0.1× salinesodium citrate and 0.5% sodium dodecyl sulfate. After XOMAT ARautoradiography film (Kodak, Rochester, N.Y.) is exposed to the blots orthe blots are placed in a PHOSPHOIMAGER cassette (Molecular Dynamics,Sunnyvale, Calif.) for several hours, hybridization patterns arecompared visually.

VII Microarrays

To produce oligonucleotides for a microarray, the nucleotide sequencedescribed herein is examined using a computer algorithm which starts atthe 3' end of the nucleotide sequence. The algorithm identifiesoligomers of defined length that are unique to the gene, have a GCcontent within a range suitable for hybridization, and lack predictedsecondary structure that would interfere with hybridization. Thealgorithm identifies 20 sequence-specific oligonucleotides of 20nucleotides in length (20-mers). A matched set of oligonucleotides iscreated in which one nucleotide in the center of each sequence isaltered. This process is repeated for each gene in the microarray, anddouble sets of twenty 20 mers are synthesized and arranged on thesurface of the silicon chip using a light-directed chemical process(Chee, M. et al., PCT/WO95/11995, incorporated herein by reference).

In the alternative, a chemical coupling procedure and an ink jet deviceare used to synthesize oligomers on the surface of a substrate(Baldeschweiler, J. D. et al., PCT/WO95125116, incorporated herein byreference). In another alternative, a "gridded" array analogous to a dot(or slot) blot is used to arrange and link cDNA fragments oroligonucleotides to the surface of a substrate using a vacuum system,thermal, UV, mechanical or chemical bonding procedures. An array may beproduced by hand or using available materials and machines and containgrids of 8 dots, 24 dots, 96 dots, 384 dots, 1536 dots or 6144 dots.After hybridization, the microarray is washed to remove nonhybridizedprobes, and a scanner is used to determine the levels and patterns offluorescence. The scanned images are examined to determine degree ofcomplementarity and the relative abundance of each oligonucleotidesequence on the micro-array.

VIII Complementary Polynucleotides

Sequence complementary to the AFB1-hAR-encoding sequence, or any partthereof, is used to decrease or inhibit expression of naturallyoccurring AFB1-hAR. Although use of oligonucleotides comprising fromabout 15 to about 30 base-pairs is described, essentially the sameprocedure is used with smaller or larger sequence fragments. Appropriateoligonucleotides are designed using OLIGO 4.06 software and the codingsequence of AFB1-hAR, SEQ ID NO:1. To inhibit transcription, acomplementary oligonucleotide is designed from the most unique 5'sequence and used to prevent promoter binding to the coding sequence. Toinhibit translation, a complementary oligonucleotide is designed toprevent ribosomal binding to the AFB1-hAR-encoding transcript.

IX Expression of AFB1-hAR

Expression of AFB1-hAR is accomplished by subcloning the cDNAs intoappropriate vectors and transforming the vectors into host cells. Inthis case, the cloning vector is also used to express AFB1-hAR in E.coli. Upstream of the cloning site, this vector contains a promoter forB3-galactosidase, followed by sequence containing the amino-terminalMet, and the subsequent seven residues of β-galactosidase. Immediatelyfollowing these eight residues is a bacteriophage promoter useful fortranscription and a linker containing a number of unique restrictionsites.

Induction of an isolated, transformed bacterial strain with IPTG usingstandard methods produces a fusion protein which consists of the firsteight residues of β-galactosidase, about 5 to 15 residues of linker, andthe full length protein. The signal residues direct the secretion ofAFB1-hAR into the bacterial growth media which can be used directly inthe following assay for activity.

X Demonstration of AFB1-hAR Activity

The reductase activity of AFB1-hAR towards 4-nitrobenzaldehyde isassayed spectrophotometrically as described by Hayes, et al. (supra).Activity of AFB1-hAR towards AFB1 is measured by the HPLC-based assaydescribed by Judah, et al. (supra).

XI Production of AFB1-hAR Specific Antibodies

AFB1-hAR that is substantially purified using PAGE electrophoresis(Sambrook, supra), or other purification techniques, is used to immunizerabbits and to produce antibodies using standard protocols. The aminoacid sequence deduced from SEQ ID NO:2 is analyzed using DNASTARsoftware (DNASTAR Inc) to determine regions of high immunogenicity and acorresponding oligopeptide is synthesized and used to raise antibodiesby means known to those of skill in the art. Selection of appropriateepitopes, such as those near the C-terminus or in hydrophilic regions,is described by Ausubel et al. (supra), and others.

Typically, the oligopeptides are 15 residues in length, synthesizedusing an Applied Biosystems peptide synthesizer model 431A usingfmoc-chemistry, and coupled to keyhole limpet hemocyanin (KLH, Sigma,St. Louis, Mo.) by reaction with N-maleimidobenzoyl-N-hydroxysuccinimideester (MBS; Ausubel et al., supra). Rabbits are immunized with theoligopeptide-KLH complex in complete Freund's adjuvant. The resultingantisera are tested for antipeptide activity, for example, by bindingthe peptide to plastic, blocking with 1% BSA, reacting with rabbitantisera, washing, and reacting with radio iodinated, goat anti-rabbitIgG.

XII Purification of Naturally Occurring AFB1-hAR Using SpecificAntibodies

Naturally occurring or recombinant AFB1-hAR is substantially purified byimmunoaffinity chromatography using antibodies specific for AFB1-hAR. Animmunoaffinity column is constructed by covalently coupling AFB1-hARantibody to an activated chromatographic resin, such as CNBr-activatedSEPHAROSE (Pharmacia & Upjohn). After the coupling, the resin is blockedand washed according to the manufacturer's instructions.

Media containing AFB1-hAR is passed over the immunoaffinity column, andthe column is washed under conditions that allow the preferentialabsorbance of AFB1-hAR (e.g., high ionic strength buffers in thepresence of detergent). The column is eluted under conditions thatdisrupt antibody/AFB1-hAR binding (eg, a buffer of pH 2-3 or a highconcentration of a chaotrope, such as urea or thiocyanate ion), andAFB1-hAR is collected.

XIII Identification of Molecules Which Interact with AFB1-hAR

AFB1-hAR or biologically active fragments thereof are labeled with ¹²⁵¹I Bolton-Hunter reagent (Bolton et al. (1973) Biochem. J. 133: 529).Candidate molecules previously arrayed in the wells of a multi-wellplate are incubated with the labeled AFB1-hAR, washed and any wells withlabeled AFB1-hAR complex are assayed. Data obtained using differentconcentrations of AFB1-hAR are used to calculate values for the number,affinity, and association of AFB1-hAR with the candidate molecules.

All publications and patents mentioned in the above specification areherein incorporated by reference. Various modifications and variationsof the described method and system of the invention will be apparent tothose skilled in the art without departing from the scope and spirit ofthe invention. Although the invention has been described in connectionwith specific preferred embodiments, it should be understood that theinvention as claimed should not be unduly limited to such specificembodiments. Indeed, various modifications of the described modes forcarrying out the invention which are obvious to those skilled inmolecular biology or related fields are intended to be within the scopeof the following claims.

    __________________________________________________________________________    #             SEQUENCE LISTING                                                   - -  - - (1) GENERAL INFORMATION:                                             - -    (iii) NUMBER OF SEQUENCES: 3                                           - -  - - (2) INFORMATION FOR SEQ ID NO:1:                                     - -      (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 331 amino - #acids                                                (B) TYPE: amino acid                                                          (C) STRANDEDNESS: single                                                      (D) TOPOLOGY: linear                                                 - -    (vii) IMMEDIATE SOURCE:                                                         (A) LIBRARY: BRAINOT14                                                        (B) CLONE: 1596452                                                   - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                               - -  Met Ser Arg Gln Leu Ser Arg Ala Arg Pro - #Ala Thr Val Leu Gly        Ala                                                                               1               5 - #                 10 - #                 15             - -  Met Glu Met Gly Arg Arg Met Asp Ala Pro - #Thr Ser Ala Ala Val Thr                   20     - #             25     - #             30                  - -  Arg Ala Phe Leu Glu Arg Gly His Thr Glu - #Ile Asp Thr Ala Phe Val               35         - #         40         - #         45                      - -  Tyr Ser Glu Gly Gln Ser Glu Thr Ile Leu - #Gly Gly Leu Gly Leu Arg           50             - #     55             - #     60                          - -  Leu Gly Gly Gly Asp Cys Arg Val Lys Ile - #Ala Thr Lys Ala Asn Pro       65                 - # 70                 - # 75                 - # 80       - -  Trp Asp Gly Lys Ser Leu Lys Pro Asp Ser - #Val Arg Ser Gln Leu Glu                       85 - #                 90 - #                 95              - -  Thr Ser Leu Lys Arg Leu Gln Cys Pro Gln - #Val Asp Leu Phe Tyr Leu                   100     - #            105     - #            110                 - -  His Thr Pro Asp His Gly Thr Pro Val Glu - #Glu Thr Leu His Ala Cys               115         - #        120         - #        125                     - -  Gln Arg Leu His Gln Glu Gly Lys Phe Val - #Glu Leu Gly Leu Ser Asn           130             - #    135             - #    140                         - -  Tyr Ala Ser Trp Glu Val Ala Glu Ile Cys - #Thr Leu Cys Lys Ser Asn       145                 - #150                 - #155                 -         #160                                                                             - -  Gly Trp Ile Leu Pro Thr Val Tyr Gln Gly - #Met Tyr Asn Ala Ile        Thr                                                                                              165 - #                170 - #                175            - -  Arg Gln Val Glu Thr Glu Leu Phe Pro Cys - #Leu Arg His Phe Gly Leu                   180     - #            185     - #            190                 - -  Arg Phe Tyr Ala Tyr Asn Pro Leu Ala Gly - #Gly Leu Leu Thr Gly Lys               195         - #        200         - #        205                     - -  Tyr Lys Tyr Glu Asp Lys Asp Gly Lys Gln - #Pro Val Gly Arg Phe Phe           210             - #    215             - #    220                         - -  Gly Asn Thr Trp Ala Glu Met Tyr Arg Asn - #Arg Tyr Trp Lys Glu His       225                 - #230                 - #235                 -         #240                                                                             - -  His Phe Glu Gly Ile Ala Leu Val Glu Lys - #Ala Leu Gln Ala Ala        Tyr                                                                                              245 - #                250 - #                255            - -  Gly Ala Ser Ala Pro Ser Val Thr Ser Ala - #Ala Leu Arg Trp Met Tyr                   260     - #            265     - #            270                 - -  His His Ser Gln Leu Gln Gly Ala His Gly - #Asp Ala Val Ile Leu Gly               275         - #        280         - #        285                     - -  Met Ser Ser Leu Glu Gln Leu Glu Gln Asn - #Leu Ala Ala Thr Glu Glu           290             - #    295             - #    300                         - -  Gly Pro Leu Glu Pro Ala Val Val Asp Ala - #Phe Asn Gln Ala Trp His       305                 - #310                 - #315                 -         #320                                                                             - -  Leu Val Ala His Glu Cys Pro Asn Tyr Phe - #Arg                                           325 - #                330                                    - -  - - (2) INFORMATION FOR SEQ ID NO:2:                                     - -      (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 1373 base - #pairs                                                (B) TYPE: nucleic acid                                                        (C) STRANDEDNESS: single                                                      (D) TOPOLOGY: linear                                                 - -    (vii) IMMEDIATE SOURCE:                                                         (A) LIBRARY: BRAINOT14                                                        (B) CLONE: 1596452                                                   - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                               - -  CGACCGCTGC GCGCGGCTCC TGGGCTGTCA CAGTCTCCCG TTGCCGCCGT - #CATGTCCC    GG    60                                                                        - -  CAGCTGTCGC GGGCCCGGCC AGCCACGGTG CTGGGCGCCA TGGAGATGGG - #GCGCCGCAT    G   120                                                                         - -  GACGCGCCCA CCAGCGCCGC AGTCACGCGC GCCTTCCTGG AGCGCGGCCA - #CACCGAGAT    A   180                                                                         - -  GACACGGCCT TCGTGTACAG CGAGGGCCAG TCCGAGACCA TCCTTGGCGG - #CCTGGGGCT    C   240                                                                         - -  CGGCTGGGCG GTGGCGACTG CAGAGTGAAA ATTGCCACCA AGGCCAACCC - #TTGGGATGG    A   300                                                                         - -  AAATCACTAA AGCCTGACAG TGTCCGGTCC CAGCTGGAGA CGTCATTGAA - #GAGGCTGCA    G   360                                                                         - -  TGTCCCCAAG TGGACCTCTT CTACCTACAC ACACCTGACC ACGGCACCCC - #GGTGGAAGA    G   420                                                                         - -  ACGCTGCATG CCTGCCAGCG GCTGCACCAG GAGGGCAAGT TCGTGGAGCT - #TGGCCTCTC    C   480                                                                         - -  AACTATGCTA GCTGGGAAGT GGCCGAGATC TGTACCCTCT GCAAGAGCAA - #TGGCTGGAT    C   540                                                                         - -  CTGCCCACTG TGTACCAGGG CATGTACAAT GCCATCACCC GGCAGGTGGA - #AACGGAGCT    C   600                                                                         - -  TTCCCCTGCC TCAGGCACTT TGGACTGAGG TTCTATGCCT ACAACCCTCT - #GGCTGGGGG    C   660                                                                         - -  CTGCTGACCG GCAAGTACAA GTATGAGGAC AAGGATGGGA AACAGCCTGT - #GGGCCGCTT    C   720                                                                         - -  TTTGGGAATA CCTGGGCAGA GATGTACAGG AATCGCTACT GGAAGGAGCA - #CCACTTCGA    G   780                                                                         - -  GGCATTGCCC TGGTGGAGAA GGCCCTGCAG GCCGCGTATG GCGCCAGCGC - #CCCCAGTGT    G   840                                                                         - -  ACCTCGGCTG CCCTCCGGTG GATGTACCAC CACTCACAGC TGCAGGGTGC - #CCACGGGGA    C   900                                                                         - -  GCGGTCATCC TGGGCATGTC CAGCCTGGAG CAGCTGGAGC AGAACTTGGC - #AGCAACAGA    G   960                                                                         - -  GAAGGGCCCC TGGAGCCGGC TGTCGTGGAT GCCTTTAATC AAGCCTGGCA - #TTTGGTTGC    T  1020                                                                         - -  CACGAATGTC CCAACTACTT CCGCTAGGCC CATCATGGCT CAGGCTGCCC - #AAGGCTTTT    C  1080                                                                         - -  TGTCACCTCT TTTGTTCTCT CACACTGACC AGTCTTGGCC TTAAGCTGAC - #TTAGAAGGG    T  1140                                                                         - -  TTTTCTGAAT TGTCTAGATC CATGCATTAT TTTTCTAGCT TCCTGCCTTG - #CTCCCTATT    C  1200                                                                         - -  ACTTTACACT GTGAAAGGTG GGGGGTGAGT CCCACTTGAG CGCTTCCTGT - #TGAATAAAG    C  1260                                                                         - -  AGGCACTTGA CCTGGCTGTA GCCTAGGTCT TGAGTGAACC CCAAAAAAAA - #AAAAAAAGG    C  1320                                                                         - -  GGCGCTACCG CGGTGAGCTC CAGCTGTGTC CCTTAGTAGG TAATTCGCCT - #GCA             1373                                                                         - -  - - (2) INFORMATION FOR SEQ ID NO:3:                                     - -      (i) SEQUENCE CHARACTERISTICS:                                                 (A) LENGTH: 327 amino - #acids                                                (B) TYPE: amino acid                                                          (C) STRANDEDNESS: single                                                      (D) TOPOLOGY: linear                                                 - -    (vii) IMMEDIATE SOURCE:                                                         (A) LIBRARY: GenBank                                                          (B) CLONE: 433611                                                    - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                               - -  Met Ser Gln Ala Arg Pro Ala Thr Val Leu - #Gly Ala Met Glu Met Gly        1               5 - #                 10 - #                 15              - -  Arg Arg Met Asp Val Thr Ser Ser Ser Ala - #Ser Val Arg Ala Phe Leu                   20     - #             25     - #             30                  - -  Gln Arg Gly His Thr Glu Ile Asp Thr Ala - #Phe Val Tyr Ala Asn Gly               35         - #         40         - #         45                      - -  Gln Ser Glu Thr Ile Leu Gly Asp Leu Gly - #Leu Gly Leu Gly Arg Ser           50             - #     55             - #     60                          - -  Gly Cys Lys Val Lys Ile Ala Thr Lys Ala - #Ala Pro Met Phe Gly Lys       65                 - # 70                 - # 75                 - # 80       - -  Thr Leu Lys Pro Ala Asp Val Arg Phe Gln - #Leu Glu Thr Ser Leu Lys                       85 - #                 90 - #                 95              - -  Arg Leu Gln Cys Pro Arg Val Asp Leu Phe - #Tyr Leu His Phe Pro Asp                   100     - #            105     - #            110                 - -  His Gly Thr Pro Ile Glu Glu Thr Leu Gln - #Ala Cys His His Val His               115         - #        120         - #        125                     - -  Gln Glu Gly Lys Phe Val Glu Leu Gly Leu - #Ser Asn Tyr Val Ser Trp           130             - #    135             - #    140                         - -  Glu Val Ala Glu Ile Cys Thr Leu Cys Lys - #Lys Asn Gly Trp Ile Met       145                 - #150                 - #155                 -         #160                                                                             - -  Pro Thr Val Tyr Gln Gly Met Tyr Asn Ala - #Ile Thr Arg Gln Val        Glu                                                                                              165 - #                170 - #                175            - -  Thr Glu Leu Phe Pro Cys Leu Arg His Phe - #Gly Leu Arg Phe Tyr Ala                   180     - #            185     - #            190                 - -  Phe Asn Pro Leu Ala Gly Gly Leu Leu Thr - #Gly Arg Tyr Lys Tyr Gln               195         - #        200         - #        205                     - -  Asp Lys Asp Gly Lys Asn Pro Glu Ser Arg - #Phe Phe Gly Asn Pro Phe           210             - #    215             - #    220                         - -  Ser Gln Leu Tyr Met Asp Arg Tyr Trp Lys - #Glu Glu His Phe Asn Gly       225                 - #230                 - #235                 -         #240                                                                             - -  Ile Ala Leu Val Glu Lys Ala Leu Lys Thr - #Thr Tyr Gly Pro Thr        Ala                                                                                              245 - #                250 - #                255            - -  Pro Ser Met Ile Ser Ala Ala Val Arg Trp - #Met Tyr His His Ser Gln                   260     - #            265     - #            270                 - -  Leu Lys Gly Thr Gln Gly Asp Ala Val Ile - #Leu Gly Met Ser Ser Leu               275         - #        280         - #        285                     - -  Glu Gln Leu Glu Gln Asn Leu Ala Leu Val - #Glu Glu Gly Pro Leu Glu           290             - #    295             - #    300                         - -  Pro Ala Val Val Asp Ala Phe Asp Gln Ala - #Trp Asn Leu Val Ala His       305                 - #310                 - #315                 -         #320                                                                             - -  Glu Cys Pro Asn Tyr Phe Arg                                                              325                                                        __________________________________________________________________________

What is claimed is:
 1. A substantially purified human aflatoxin B1aldehyde reductase comprising the amino acid sequence of SEQ ID No:1 ora fragment of SEQ ID No:1, wherein said fragment maintains aflatoxin B1aldehyde reductase activity.
 2. A composition comprising thesubstantially purified human aflatoxin B1 aldehyde reductase of claim 1.